Everything should give MP during ice because the whole point was to replace server ticks, which you can't really keep track of easily and them arbitrarily and semi-randomly not aligning with your rotation. And one tick is close enough to one GCD. I.e. to fix the actual issue you were aiming to fix, unpredictable ticks, every GCD should restore MP for more predictable regeneration in about the same duration.
Otherwise you are just doing the unfortunate thing they ended up doing: Messing about with something that wasn't broken.
