In the past few weeks I made some developments on the alternative solutions.
First I made a hardware decoder for timecode signal, which eliminates the analog audio processing in software or firmware. And I also added an external I2S DAC to the system to be able to use and test all 4 channels of audio. Here is a video of the new hardwarare unit. It is still the MIDI controls the iPad application but the midi signal is made directly from the vinyl audio.
This is the hardware decoder for timecode signal. It is more or less a RIAA corrector and comparator for sine wave. The tricky part is that it works with a single 5V supply of USB port and it is more or less independent of the signal amplitude coming from the cartridge during fast and slow vinyl moves.
The other improvement I made is my 3D printed stand for the optical mous PCB which is here: