One way to get 32 counties, IMVHO, is this:
POD: Archhduke Franz Ferdinand doesn't get shot on schedule, lighting the powder train.
Thus, Home Rule doesn't get postponed due to the war.
Carston had plans to rebel against an Irish government--which would have been a bloody mess. There would have been dificulty putting his rebellion down, as there might have been British soldiers unwilling to fight.
As things are brewing--a Parliament in Dublin is formed, there's unrest, or even rebellion, in Protestant portions of Ulster, and things are on the edge of blowing up...someone else lights Europe's fuse.
With Europe going up in flames, Britian HAS to squelch the problems FAST--and the Dublin government now has firepower to make it easier for Britain to squish the Protestant rebels than the legitimate Dublin government.
Things could go from there, leading to a united Ireland postwar.
This would ned LOTS of work to make it a timeline--but perhaps something could be done...
While there was the Curragh mutiny in, I think if war hadn't been gathering the MOD would have relieved the officers and used other Imperial officers to carry out the orders.
The one problem of using force to suppress the Ulster area is that this would lead to significant problems after the war, I have the same doubts about a situation of the 26 counties getting the 6 after WW2, it's adding the Troubles to Ireland and would call for significant internal security, while reducing the productivity in Ulster.