He did do that. But William came over and won the
resulting war, which is essentially the root of the Protestant vs Catholic division in Ireland. Are you proposing that William loses this war and leaves Ireland in Stuart hands? Or are you proposing that James goes straight to Ireland rather than via France (I don't think that would work, as he really needed French backing to have a fighting chance).
I'm not sure if it's sustainable in the long run, but in the short term, French backing could preserve that arrangement, especially if England has problems with the Jacobites in Scotland and a constitutional crisis over the succession.
Notably, in OTL James II was spectacularly ungrateful to his Irish supporters after losing the war, blaming
them for his position...