I am new to Bittle and have just received a unit and so far have just operated it with the IR remote.
I did do some reading on your challenges page that sound super interesting. I did notice that 1 of the biggest restraints is the MCU processing power and available RAM. I have also noticed that an ESP32 main board is under development and this will fix this problem but will add a new problem that ESP32 has very low pin count. I also notice that your currently using a PCA9685 IC to create the PWM signals for servo control. The PCA9685 is driven via I2C which is a very slow protocol, I am not sure whether your using the MPU6050 in I2C mode or SPI mode (all the quad-copter drones use SPI mode for faster feed back loops).
Have you looked at the K210 MCU? It is a dual core 64bit RISC-V chip clocked at 400MHz (most people have been over clocking to 600MHZ) with a number of hardware accelerators and lots of RAM and large pin count. Having a fast MCU with lots of pins means you won't need the PCA9685 as the PWM can be generated by the timers on the MCU meaning very fast updates compared to an external I2C chip. The K210 also has it's own parallel camera, LCD and mic peripheral as it is desinged to run AI on the edge.