From what I understood the Vampire is a FPGA board where one CPU must do everything. No custom shipsets like Amiga had.
In that scence the Pi is more Amiga like. So much is done with the GPU these days. Video, 3D, 2D.
SMP is very difficult without breaking everything. It is still possibly a good idea to fork AROS and have a version people can play with on top of the classic version. It is what Mschulz is doing. I'm quite sure he got it right. I'm more unsure about where a forked AROS version is going. Just look at Haiku and how many years that OS been in development without any success. Where does a new OS fit inn and how long are people going to wait for it to be usable.
AROS just recently, with the right hardware became a stable, good OS.
Personaly and at least for now I like the x86 series. Still with single core that CPU is very powerfull. write or port some drivers for some powerfull GPU and we would have a system that would fly. I'm even happy with my Latitude D520. With 2 GHz Core2Duo CPU and at least good 2D accelleration I enjoy it. 3D chip is quite weak but still good to play some of the older 3D games like Quake III in lower resolutions.
There are no arm CPU today that could touch even a Core2Duo CPU running single core, maybe in the future. The GPU in Pi is way more powerfull than the IntelGMA GPU in my laptop. Let's see if there ever will be a native drivers for Pi GPU running AROS. Problem might be with next Pi new GPU would need new drivers.
Look at Amiga, MorphOS and AROS. How many drivers do we got for different hardware. Not may. It is no easy task. The introduction of Nouveau, MESA solved lot's of that, at least for GPUs but not been updated in long time. It's been so long time that there are no Laptop made last 10 - 12 years that would work with it.