I think it's better than just changing up based on whatever direction the character is involved in or slowly phasing out the former.
Of course, it's not gonna be just for the protagonist, others will have this trait at limited extent with more chemistry involved.
This discourse of Sonic's signature element being in constant flux...
it reminds of the time when I decided that i wanted the protagonist (for my personal original project) to have some standard cyan energy that can shift into different effects.
Like it can shift into something that acts like flame, flow like water, or sparks like electricity. Despite the different behaviors, the only thing that will be retained is the base element of the character.