First of all, I’m happy to hear, that you are enjoying our product.
Secondly, not sure what you really need, if you could explain better would be nice.
To straight things up, at this point, a low-level robot controller (core2) subscribes to velocity commands (/cmd_vel). PID, forward/inverse kinematics are calculated there so there would be a perfect place to make a controller using raw data, but I think it might be complicated to mess with firmware.
My idea is that you can build a simple Kalman filter using SS model and compare results to EKF. Second taught is to tune a little firmware giving it the ability to share data for every wheel separately and build a high-level python controller.
What do you think?