Obviously someone has no idea how these processors are programmed.
The person who brought up the compiler issue, stated so when I made same case for starting from scratch on a new OS and existing hardware. Basically saying those are not a single use processor, so compiler config needs to perfectly match the boards other hardware, drivers, ect. Which equals a lot more time to reverse for starters. I can't verify, since I've never cracked one open, or played with a J-tag tool on these ECU's. But the source is well respected.
I do agree there should be a way to do it, with a little help. The E35, best known to rest of world by another manufacture part# I can't recall, would be a great starting point. It was also used by MB and others. However I once attempted to load a LBZ OS to E35B and LMM to E35A version just for chits and giggles. It actually loads about 90% of the bin, then soft bricks.. So there is obviously some memory mapping differences between those two.
Also ran into similar issues on the GM E38, by installing the wrong year OS file with Tech2. It powers up, runs fine on bench, but shows as locked with no SN or VIN when you try to read/write again. Is a documented memory allocation issue, based on year, using same hardware. So at a min the bootloader is diff.
I've been working with a new stand alone ECU manufacture I met at PRI on unrelated project. I'll find out what's actually involved in driving 50volt injectors, and if they have any interest. Also my friend across the pond said check out this manufacture.
https://www.huber-automotive.com/services/?lang=en