x86 sounds good at first, but then you will also need things like WINE and directx to boost the the software for it. Otherwise you will have to wait for people to port software. It means years before you can do anything with it. AROS is as good as it gets here.
There 'could' be a market for it on ARM devices though. It could have a niche in between the alternatives. It has plenty of games and apps to bring across with it.
I would certainly prefer a customisable Amiga OS on my smartphone or in a simple portable computer.