UchihaFanatic
Isn't grappling ninjas in Naruto world a bit dangerous? I mean any decently trained ninja could use substitution right? Imagine pinning someone and they would suddenly turn into sand or something worse like poisoned bugs, poisoned snakes, poisoned puppets, poisoned puppies etc. Not to mention techniques similar to jirayas' needle hair, or people that detonate themselves. Buut there's a lot of inconsistencies in Naruto so you could probably still make it work somehow.
Seimei kikan abilities that you have is actually one of Canon abilities, but with freedom to add more strength by buffing up muscle or more speed by thinning the muscle with default compress muscle of perfect strength and speed proportion. Seimei kikan in easy word, a metabolism technique. Its functions by you eating tons of food without getting bloat because the technique fasten your metabolism and instantly change what you eat into energy stored inside your body. Then the energy will fuel whatever you do with seimei kikan which is controlling the body part you normally cannot control like hair length, speed of healing, muscle compression and buff/lean according to your wish, endless stamina and endurance, etc..