From time to time I wonder if there is a market for refurbishing circuit boards from higher end old cars. When I had my analog three gun CRT for video, there were a series of standard fixes we would do - primarily replacing "leaky" capacitors with good quality Japanese capacitors, and reflowing oxidized solder joints on printed circuit boards. The resistors and ICs generally held up well. Of course, testing was extremely time consuming because you often had to remove components from the PCB to test, and once you made a repair, you were using your video projector to test. For capacitors, it was more efficient to just replace them all.
To be efficient on automotive circuit boards, you would need either detailed information of the failure points, or better yet, schematics. And you would have to develop testing procedures to test boards outside of the cars. That said, I could teach a teenager to do the work once the procedures were set up.
I have heard that there is a guy who does the e31 circuit boards, so there may be an opportunity...