Actually Fiz I do know what I'm talking about.
I think AmigaOS 4's best chance of survival is not emulation or on x86, but on an open design based on the NUMA architecture ( Basically it is a decentralised DMA system which is widely copied, Intel uses QPI which takes a lot of the same ideas ) and I fully support breaking both API and ABI as well as architectural compatibility for a sustainable architecture. Both MIPS and SPARC have open designs, which means A-EON could improve them without a license.
The primary advantages of AmigaOS are that it is lightweight without being impractical, and that has nothing to do with its backwards compatibility. Instead, make the OS fully 64-bit and use FS-UAE as an integrated sandbox for old software, add a ports system like in BSD as well as a frontend to it, which will make software dependency and distribution easy, NUMA architecture would increase bus performance and make a CPU that isnt as fast be less of a hindrance. CPU frequency is pretty much BS when a 1GHZ R16000A MIPS CPU wipes the floor with a 3GHz Pentium 4, all higher frequency does is make more heat and power consumption.
The only reason I don't support ARM is that up until recently most designs have been 32-bit, which in today's world of cheap memory doesn't make sense. In addition most ARM CPUs are for mobile and embedded devices. I have a Nexus 7 tablet, I love it, but it isn't any better than my 600MHz Octane2 at computational tasks, however in memory access and graphics, there is no contest, but that is to be expected.