I originally learned how to program in Ren'Py by 'finishing' a partial game, adding a bunch of content for the quasi-romance branch and a few different endings. If you're really into your idea, I left the code for Unstable Frienemies in plaintext so that it could be played with and tinkered for homebrews (or some light cheating) as the player / end-user desires.
You can even make modifications with baseline text editors - "notepad" suffices - you don't need the (free) Ren'Py utility to modify an existing game like this one. Maybe you would like to try your hand at making a branch of the game you'd like to see?