I am actually watching Michael Collins right now. Well at the time of his death Michael Collins was in effect dictator of Ireland, many will argue that. He was commander-in-chief of the Army and even though Arthur Griffith was president of the 2nd Dail however there were really three separate government in Ireland at the time creating quite the mess there was:
The Dail and its president, Arthur Griffith (whos government was intertwined with the provisional) The Provisional Government and its leader Michael Collins, and finally De Velara's Irish Republic(the anti-treaty side)
Michael collins in theory passed off his authority as Prime Minister of the Provisional government, when Arthur Griffith died Collins was the only one with the power to hold both the Dail government and the provisional together.
Collins would be President of the Dail, Prime Minister of the Provisional Government, and Commander-in-Chief of the National Army.
Very soon Collins will be able to end the military aspect of the civil war. Collins, while some of this forum painted him as a british collaborator, was no friend of the British and would rid those shackles as soon as possible, he was shipping arms and money to the IRA (both treaty/anti-treaty) forces in Northern Ireland and was already positioning the Provisional government to repeal the treaty.
de Velara will reappear in the government, but not for a while with Collins and him reconciling. The Free State will be less hectic with Collins wielding so much power. We might even see him stay in power for decades(remember he was 30 when he died)
I've actually been working on a rough draft of a Timeline including Collins surviving.