I'm going to be very blunt here, because you need to hear this to go forward :
You HAVE TO be at least API-compatible with Polars or Pandas to exist. Being backend-compatible with arrow is not enough.
There is no technical reason why you would not pick one and go with it, apart from being a very difficult task.
As of today, I have 2 major pains : Pandas being a giant memory hog and Polars not being a drop-in replacement for Pandas. I am pushing Polars, as hard as I can in all projects I can touch, and it's a very long way from being the default DataFrame library. Data Scientists will continue to use Pandas for the foreseeable future, and that saddens me greatly because I will also have to work with OOMKilled pipelines for the foreseeable future.
There is no place for a 3rd alternative, so either you become a "distribution bridge for Polars", and that would be absolutely amazing. Or, you go your own way, I'll put a small star on github, a "Noice!" in the comment section and move on and never come back.
It's tough, but sadly real.