hmm, i guess i didn’t fully understand what you are going for.
so far it seems to me like it is basically about making a custom paint brush without actually creating one and being able to use it on the fly. in principle i’m not against it - as someone who uses a tablet the less shortcuts the better.
but you might want to elaborate on how it should work step by step and how to implement it - you certainly don’t want it to clash with already established behaviour. for instance arrow keys are for moving between frames and layers - i personally don’t like it, but i’d bet many users are used to it by now.