The question as to what Gandhi may have done in Pirabaharan's timespace is an interesting and important one. I can only conjecture.
Given Gandhi's deep commitment to non violence, I would imagine that he would have sought to mobilise the Tamil people to disobey the unjust laws that discriminated against them and he would have launched a civil disobedience movement to secure freedom from alien Sinhala rule.
Initially, he would have been attacked in the same way as the Tamil satyagrahis in Colombo were attacked in 1956 when they protested against the Sinhala Only Act:
"What happened on 6 June 1956 when the Sinhala Only Bill was being debated in Parliament? The members of the Federal Party, exercising their undoubted constitutional right, wanted to protest against the imposition of (the Sinhala Only) Bill. The Members of the Federal Party said that they would sit in silence on the Galle Face Green... It was a silent protest which they were entitled to make. What happened? Hooligans, in the very presence of Parliament House, under the very nose of the Prime Minister of this country, set upon those innocent men seated there, bit their ears and beat them up mercilessly. ...
"Thereafter on that day, 6 June, every Tamil man was set upon and robbed. He was beaten up. His fountain pen and wristlet were snatched away. He was thrashed mercilessly, humiliated and sent home. The police were looking on while all this was happening before their very eyes. Shops were looted... but the police did nothing... These (hooligans) were instigated by some members of Parliament... they were heading the gang of hooligans. The Prime Minister made a remarkably wonderful speech on that occasion. He came, he smiled and he told the crowd, 'Don't do that. Rain is coming down. They will be cooled in no time.' That was the type of appeal he made. If Sinhalese men were being thrashed by Tamils and their ears bitten, I wonder whether the Prime Minister would have adopted the same attitude." (Senator S.Nadesan Q.C., Sri Lanka Senate Hansard 4 June 1958)
Again, Gandhi may have led a salt march from Jaffna to the shores of Batticaloa to establish the sovereignty of the Tamil homeland and he may have been attacked by Sinhala mobs in the same way as those travelling to the Tamil Federal Party convention in Trincomalee were attacked in 1958:
"The (Tamil) Federal Party's annual public meeting was called for late May (1958). The conclave was to decide whether or not to undertake a Satyagraha campaign now that the (Sinhala) Prime Minister had withdrawn his support from the agreement he had endorsed a year before (the Bandaranaike Chelvanayagam Pact).
"The outbreak of violence began when a train, presumed to be carrying Tamil delegates to the meetings, was derailed and its passengers beaten up by ruffians. The next day Sinhalese labourers set fire to Tamil shops and homes in nearby villages where they lived intermingled with Sinhalese...
"Arson and beatings spread rapidly to Colombo. Gangs roamed the districts where Tamils lived, ransacking and setting fire to homes and cars, and looting shops. Individual Tamils were attacked, humiliated and beaten. Many were subjected to torture and some killed outright... "
"Some ten thousand Tamils were reported to have fled their homes to seek safety in improvised refugee camps... Many fled to the North by sea.."(Professor Howard Wriggins: Ceylon - Dilemmas of a New Nation, Princeton University Press)
And as Gandhi persisted in his struggle, he may have been imprisoned. But, the one thing that Gandhi would not have done would have been to contest a Parliamentary seat. One can hardly see Mahatma Gandhi taking office as the Leader of the Opposition in Sri Lanka's Parliament.
But, as Gandhi's non violent campaign secured more and more adherents, the Sinhala dominated Sri Lanka government may have unleashed a 1983 type genocidal attack on the Tamil people:
"...Clearly (1983) was not a spontaneous upsurge of communal hatred among the Sinhala people.. It was a series of deliberate acts, executed in accordance with a concerted plan, conceived and organised well in advance.... Communal riots in which Tamils are killed, maimed, robbed and rendered homeless are no longer isolated episodes; they are beginning to become a pernicious habit." (Paul Sieghart: Report of a Mission to Sri Lanka on behalf of the International Commission of Jurists, March 1984)
Gandhi himself may have been charged for sedition under Sri Lanka's 6th Constitutional Amendment for advocating a separate state, even though such advocacy was by peaceful non violent means:
"...The key to its (the 6th Amendment's) effect is paragraph (1) which runs as follows:- 'No person shall directly or indirectly, in or outside Sri Lanka, support, espouse, promote, finance, encourage or advocate the establishment of a separate State within the territory of Sri Lanka'. Anyone who contravenes that provision becomes liable to the imposition of civic disability for upto 7 years, the forfeiture of his movable and immovable property... the loss of his passport... the right to engage in any trade or profession. In addition if he is a Member of Parliament, he loses his seat."
"The freedom to express political opinions, to seek to persuade others of their merits, to seek to have them represented in Parliament, and thereafter seek Parliament to give effect to them, are all fundamental to democracy itself. These are precisely the freedoms which Article 25 (of the International Covenant of Civil and Political Rights) recognises and guarantees - and in respect of advocacy for the establishment of an independent Tamil State in Sri Lanka, those which the 6th Amendment is designed to outlaw.
"It therefore appears to me plain that this enactment constitutes a clear violation by Sri Lanka of its obligations in international law under the Covenant ..." (Paul Sieghart: Report of a Mission to Sri Lanka in January 1984 on behalf of the International Commission of Jurists, March 1984)
Gandhi may have been sentenced to prison for sedition and may have been killed in a convenient 'prison riot' in the same way as Thangathurai and Kuttimuni were killed inside Welikade jail in 1983:
"Selvarajah Yogachandran, popularly known as Kuttimuni, a nominated member of the Sri Lankan Parliament... one of the 52 prisoners killed in the maximum security Welikade prison in Colombo two weeks ago, (on July 25) was forced to kneel in his cell, where he was under solitary confinement, by his assailants and ordered to pray to them. When he refused, he was taunted by his tormentors about his last wish, when he was sentenced to death. He had willed that his eyes be donated to some one so that at least that person would see an independent Tamil Eelam. The assailants then gouged his eyes...He was then stabbed to death and his testicles were wrenched from his body. This was confirmed by one of the doctors who had conducted the postmortem of the first group of 35 prisoners." (Madras Hindu, 10 August 1983)
And, ofcourse, if Gandhi had fasted, the fate that befell Thileepan and Annai Poopathy may have fallen on him - and Gandhi would have been allowed to die, and labelled as an unreasonable trouble maker, who had not accepted the compromise of Provincial Councils instead of insisting on freedom, and who by his actions was fomenting unrest which would spiral out of his control.
And Sri Lanka Foreign Minister Lakshman Kadirgamar (to use the temperate language that he has recently used in respect of Pirabaharan) may have called Gandhi a "suicidal, maniacal kind of a man who would ultimately prefer to bring his whole house down rather than give in."
But in his death, Gandhi would not have failed - just as much as Thileepan and Annai Poopathy have not failed in their deaths. As Aurobindo wrote many years ago on ideas such as freedom:
"The idea creates its martyrs. And in martyrdom there is an incalculable spiritual magnetism which works miracles. A whole nation, a whole world catches the fire which burned in a few hearts; the soil which has drunk the blood of the martyr imbibes with it a sort of divine madness which it breathes into the heart of all its children, until there is but one overmastering idea, one imperishable resolution in the minds of all besides which all other hopes and interests fade into significance and until it is fulfilled, there can be no peace or rest for the land or its rulers.
It is at this moment that the idea creates its heroes and fighters, whose numbers and courage defeat only multiplies and confirms until the idea militant has become the idea triumphant. Such is the history of the idea, so invariable in its broad outlines that it is evidently the working of a natural law...
But the despot will not recognise this superiority, the teachings of history have no meaning for him. ..He is deceived also by the temporary triumph of his repressive measures.. and thinks, “Oh, the circumstances in my case are quite different, I am a different thing from any yet recorded in history, stronger, more virtuous and moral, better organised. I am God’s favourite and can never come to harm.” And so the old drama is staged again and acted till it reaches the old catastrophe..."
And Gandhi, perhaps, would have said of Pirabaharan, as he had said of Baghat Singh:
"His way is not my way, but I bow my head before one who is prepared to give his life for the freedom of his people."
And, here I may be wrong, (and as I have said, I can only conjecture) I believe that Gandhi would have also recognised that the cyanide capsule in the hands of the Liberation Tigers of Tamil Eelam was evidence not of a simple minded willingness of a suicide to die but of a fierce determination that cried out: ''I will not lose my freedom except with my life'' and that it was this determination and this willingness to suffer, this thyagam, which had found an answering response in the hearts and minds of hundreds of thousands of Tamils living in many lands and across distant seas.