Thanks for the reply's I really appreciate the help.
here are some of my thoughts on the restrictions:
poison can only put you down to 1/2 a heart and it would be easily countered by carrying around a bucket of milk (not hard to acquire and people should already be carrying one because of weakness and slowness can change the tide of battle)
harming, power, sharpness and protection are interlinked so i can see why they are all limited
power, projectile protection and infinity the same as above ^
strength, ender pearls, god apples and invisibility are just OP