I'm very interested in this concept. It took me a few reads to get the way that turns progress but I think in an in game tutorial this could be easily cleared up. Like some of the other commenters, I too worry about the scope making a new board game from the ground up is a lot of work and then also making it into a game is a lot of work. I see that you made Ludochess last year so you definitely have some experience in this realm though. I really love the use of time as a resource, it fits into a theme of performance and combat.
In regards to your 2d vs 1d question, I am personally trying very hard to not overscope in this game jam. It has consistently been my downfall every game jam. So my advice is to consider the work that would be required for 2D, it might be really cool but could also be an incentive to work towards in Tempo Battle Stage 2. But that's just me, you may have different difficulties than me.
I didn't see any direct descriptions of the character's themes but I'm picturing like battling bards characters from your description. I look forward to seeing where the game goes from here! Good luck!