Modular Abilities really only allows for Creature Features and occasionally some other things. I'd be wary of letting you potentially get Refinements with it.
This. Mostly anyway. Modular Abilities is actually pretty limited, but it does allow all Strength, Speed, and Toughness powers in addition to Creature Features. It does not, however, allow
any power, and certainly not spellcraft. Nor would I allow it to, that gets broken real quick.
Now, if using custom powers, there's a construct for what you're talking about...but I try not to do that for the most part, and I remain deeply concerned about the potential abuses of being able to shuffle your Refinements at will, which is something that build would allow.