Issue is also that you would need the low level drivers in order to compile whatever modified UI was created. It is possible without the source to create a compatible development environment with open source tools but would take a lot of time. I am also sure there are be-spoke proprietary drivers that would have to be written.
It is possible to just flash the pieces that need to be changed- or even have a day night mode (i.e. same graphics but a white and black background like the roadshow cars). Someone would have to take the ROM file off an existing CIU, de-compile it and then modify the hex files that control these modes. We know that "day mode"is still in there (masked) because sometimes the maps go white as a glitch.
Anyway, it is probably possible but it also depends what the goal is. Just white background for day and black background for night or a more significant UI rehaul?
Then you have the issue of validation, which would take a ton of time because you could potentially introduce a buffer overflow which could corrupt some of the other vehicle modules.
The easier play IMO, would be to get them to release the buggy beta software with the caveat that you are using it at your own peril. Why re-invent the wheel when the software exists? Very unlikely a more stable CIU SW can be created with limited tools. Still don't understand why this software cannot be improved to make it more stable. A much better place to start than from essentially scratch, with 510. YMMV