What you want is simply not feasible. You're asking them to completely redo an enhancement tree from the ground up. And your suggestions make it look like a thief acrobat tree with monk-themed abilities. This adds nothing new to the game, only more of the same. That's like giving fighter the weapon master tree, which is so similar to kensei they might as well be the same thing.
I'm not talking about turning henshin into some sort of fire savant sorcerer, nor do I want it to have that kind of power. As it stands now, henshin is a hybrid melee/magic dps, which fails terribly due to poorly designed mechanics. I say keep it a hybrid melee/magic dps tree, but beef it up so it actually functions like it should. If you want to be a purely physical staff-wielder, then go play a thief acrobat and stop trying to turn henshin mystic into one.