Most of what the op is trying to accomplish seems like bosch ecu.
- bootloader not so needed as these ecu’s typically just need tp2 protocol or UDS for newer.
- Cal sections, seems like he has this covered with winols.
- file checksums, covered if winols likely.
OP needs to basically integrate transport(TP2) on hardware ideally, let PC control the application(kwp2000), can bus. Kline needs to have similar hardware code written as well if doing older bosch. You also need to know how to handle seed key security for programming mode, flash file encryption/compression methods, and block checksum for block flash verification. TPROT passwords can be read by OBD, but you need bootstrap loader to actually utilize them and do bootmode flashes. You can bypass TPROT entirely via OBD with some IDA work. Its a large undertaking, and a lot of “secret” knowledge involved.
You can do it all as said like J2534 passthrough, via the PC. J2534’s major downfall in my opinion is that you have to always poll for messages, no possible event for message received, so you must be crafty with threading to accomplish reading thread, and handlers that way. It can be done(ive done it).
If you go either route, i agree in the amount of hours others have said, 1000-2000. You can maybe be lucky and get some of the information required if you search well on internet and understand programming well. IDA is tremendous help along with matching .a2l files.
Best of luck!