The title is pretty self explanatory. I love My Hero Academia and one thing I like about it is that some characters started with not so amazing or so powerful Quirks [powers] and with training they were able to make them stronger or evolve into something beyond their initial understanding.

For example, the Vigilantes character Koichi Haimawari started with a power that allowed him to simply slide over surfaces, but with training he was able to evolve it into a version similar to Skids powers (maybe even a little better, with long range attacks and more).

I feel like with some of the latest students introduced we hadn't gotten the chance to witness their power evolve because they have been reduced to wallpaper after some appearances. With the New Murants and Gen X mutants there was a little more development on this aspect.

So my question is: how would you allow them to strengthen their powers or discover new aspects of their powers (like Goldballs making eggs or Rockslide being a psionic entity for example) that they didn't know about BUT without adding secondary mutations or making their powers something completely different?

I'm talking about characters like Glob, Bling!, Beak, Primal, Transonic etc. who don't have them flashy powers.