This module is way complicated to make than what you thought, I ended up bought two TDS2CM modules with $100+ each, and reverse engineered them completely by myself, please remember that you will need to decode the PLD on the original module, and find out what exactly the firmware is doing during scope boot and during RS232 communication, the 1st TDS2CM module was broken after too many experiments, and I have to bought another one to continue my project.
Picture attached is the 1st prototype I made to verify the concept, as you can see that there are lots of blue-wire to correct the mistake and verify the solution. I can give you an example how difficult to debug the issue encountered: after the module finally can be recognized by scope, the communication with PC is not stable somehow, sometimes it can be identified by PC, sometimes not, that frustrated me a lot. After weeks of debug, it ended up that the UART transceiver (SCN68681) has a limitation which requires the serial resistance of 3.6864M crystal to be <180 ohm and the shunt capacitance to be < 15pF, otherwise the oscillator may have power-up failure. after trying couple of different type of 3.6864M crystals, I finally found one that perfectly meet the requirements.
After this issue got resolved, I realized that this module is component depended (PLD and UART transceiver etc.), it can't be simply reproduced with schematic and PLD firmware, if somebody want to create one as what I did, he may encounter different issues which I may not be able help because I don't the exactly same hardware he has, not even mention that it's not worth to just make one module from cost perspective.