> It's doable but has limited benefits when they're limited to 2-4 GB of RAM anyway.

Back in the day there was no real benefit. Today it's different as most Linux distros don't really care much about supporting 32 bit anymore.

The VAIO P and some Panasonic rugged handhelds have those chips, both interesting machines, I think it would be possible to write a modern Mesa driver for those but it would be a lot of work.