On the other hand hobbling a system to run 16 year old software is silly. Run classic software in UAE and abandon the constraints that are killing the Amiga. Either you develop new software to do new things or the whole point of faster more modern systems is moot.
Dpaint IV will run faster on my Mac Pro than an X1000, but it still isn't going to replace photoshop as my daily image editor...
Take OS4, throw out the outdated concepts and bring it into 2011. Move to X86 and be done with it. The CPU has zero relevance on how "different" an operating system is.
Seamless compatibility with existing software? How useful will a lightening-fast system be without much software to run on it?