Personally, I think you would have the most chance amongst the Gaelo-Norman lords of the Pale, and of these the FitzGeralds of Desmond and Molested had the most prestige. Unfortunately, the FitzGeralds were rather loyal to the English crown at this point. John FitzGerald might be the best chance if you can sour his relations with Edward II.
You might also want to look at the various branches of the O'Neil family, but I'm unsure their standing at this point.
Honestly, if you really want to see an independent Ireland at this point, your best bet might be to have a different brother of Robert the Bruce survive. Edward was such an idiot.
Noted for the Anglo-norman lords, and the O'Neil's. Since it is, after all, Edward II who is king of England it should be fairly easy to mare anyone relation with England. Did you have any idea wich one of them could be well placed to gain the Bruce support in their quest for independance?
I always interpreted Edward nomination as a way for Bruce to de facto rule Ireland, wich will be the case with another Bruce brother too, was I wrong?
You make me think of the problem in a new light, the scenario I have in mind have Bruce realise two things:
1. To really have the Irish rise against England you need to propose something better then just go under Scotland instead, an ally instead of a defacto vassal.
2. The long term safety of Scotland demand that England be weakened, especially in Ireland and Wales, if not Scotland will always be the missing pieces of the British puzzle for London.
Is it ASB?