The MIPS + Uae idea looks to be the simplest, quickest and cheapest way of getting this product idea to market - as suggested by bloodline - which only leaves getting licenses for games.
However, a prototype shouldnt be too hard to knock up, which could run games that we already have single licenses for.
Running Uae ontop of another OS seems practical, especially if a little extra time is taken to make the os, say linux, small, lightweight and can boot quickly - almost becoming invisible to the consumer. This isnt too difficult to do as linux is excellent in embedded devices.
Once a prototype is ready, it could be demo'd at Amiga Shows (tho the device is more aimed at any home users, rather than amiga followers) and then aim to get some financial backing and get IP issues sorted.
I'd be interested in working on such a project.
Samuar
Edit/Addition:
The Sega Dreamcast uses a SuperH processor as opposed to a MIPS. However, with a bit of hardware and software work, it could be used as a proof of theory concept prototype.