I hate to come back to this point, but:
If AROS would only support ATI RV360, will be the need to worry about drivers? A single interface, extremely optimized could be built, and then, maybe, a full sdk above it.
Then, some skilled programmers, could even access the RV360 directly to create some old-time experience. Just like what was done at the 80's.
For example, the AROS team, could dictate:
"Amigros 1800" consists on the following restricted hardware: Motherboard Soyo XPTO, Athlon 64 core YZK, ATI RV360 chip, soundblaster model XXRRROOO and etc...
If you want to be able to run "AROS 2.7" and all the software made to it, you MUST meet exactly this HW requirements.