It looks like you're developing toward something cool here! I think a JRPG-style battle system should be doable within the timeframe of the jam, so that seems like a good choice. Let me know if you'd like to exchange feedback on pixel art, since I'll be using that for my project as well!
Sounds like your ideas are still pretty broad at this stage, but I wish you the best as you narrow in on a specific story and style! Looking forward to giving it a try a few weeks down the road :)