Hello! That sounds like a very clever idea.
If the features on the painting of the protagonist are vague enough this will be allowed. I’d highly encourage you to think how you can convey this is the protagonist while working with the limitation of trying to make those as simplistic as possible.
Follow the mentality of the silhouettes. What is the Minimum viable protagonist-lifestage -representation? Maybe using a defining colour for the protagonist???
This will be hopefully a challenging limitation that will make you push your limits in abstraction.