Contrafactuals are always tricky, and I am far from informed enough to really argue one way or the other.

But if I understand the basic setting in the late 60ies and early 70ies it is to a large extent the local unionist that uses their positions of power in local government and strategic unions to undermine progress the local catholics is making. And the UK government is reluctant to use state violence against the unionists who therefore gets away with using violence against the catholics, and once UK forces are sent in the are almost only used against the catholic inhabitants.

If so, it would be possible that the IRA violence is either a) what brings the unionists to the table or b) what makes the UK government bring the unionists to the table. And even though the IRA did not and probably could not succeed in getting bring about unification through violence, through the GFA the plain field has been changed enough to make a non-violent unification possible, which wasn't possible before.

In a sense (and a bit inspired by Graeber), the argument would be that through a violent campaign, where teh ulitmate goal is doomed to fail, the balance of structural violence underpinning the state structure was somewhat shifted.

But as I said above, to actually make that argument one would have to have more knowledge about the situation and to really argue a or b one would ideally also have access to decisionmakers diaries, private letters, memorandums etc. Perhaps some of the sources from the early 70ies are availble now, but I doubt critical sources from the 90ies are availble.