x86 is the commonest platform so it should be on it. Go full 64-bit SMP/SMT while your at it.
I would also like to see it on ARM because it is perfect for light lean OS and unlike other ARM OS you would be free to tinker with it.
PowerPC died when Apple dumped it, if people didn't see it was time to move then... they must interpret the world funny.
68k on FPGA will be satisfactory, but it is not for a serious alternative main OS.
If nothing happens I hope Haiku or AROS will be fully functional alternative OSes.
Sorry to pick on you, just quoting to address a general misconception, but PPC compatible cores are in Wii/PS3/360....and you can thank IBM not those twats at Apple

Last Amiga died with A4000/A1200. All the others are just Amiga by name, no custom chips and no style just a box for running OS4 (which needs a LOT of work to catch up)
(CELL PPU is more or less 1 Xenon core)