Dear customer,
Your approach for the device in scope of this project is an interesting idea, though the OBD2 protocol does not support this "save" of the stream because there is a handshake to confirm the sent values is acknowledged by the vehicle. As you described ""simulate vehicle" and to comply with OBD2 protocol means literally to reverse engineer the entire ECUs software that you intend to program. And we also need to remind nowadays vehicles are equipped with tens of ECUs. Yes sending an stream of data not parsed via USB is a simple task, but the "vehicle emulation" is not just sending the identification model&VIN.
More than that, most of the code will be embedded, so it doesn't really matter what language will be used in the compiler,because the final code to be written in HW will be hex.
The final result can be achieved, but for sure not by the people who placed the bids by now- please just evaluate their proposals descriptions and you will conclude by yourself.
I propose to you different approach,that may be solution to your problem, but we need to discuss before starting the project together. My technical advice to you will be entirely free, but in this way you will know better what options you have for your needed device.