I would say the easiest way to do it is to simply give them the same Atk/Acc as an A+ with the weapon they are using, so for all of them at 99 they would have the same Acc as any job using a weapon with capped skill(424) and then as they go up through item levels simply add what that level would have on a weapon up till 119 where it could be 228~242. Right now it seems like they intentionally gimp their accuracy. Our jobs shouldn't be taken into account, our stats shouldn't be taken into account, the only thing that should matter is our gear when we summon them, and truly I wish it to be solely based on our weapon when we summon them.