The advantages of ARM that you list are advantages for smartphone manufacturers. The morphOS team aren't going to build hardware.

Frankly the obsession with this or that CPU architecture is a waste of time. They're all fast enough. The correct choice is to port to the one that's standard and easily available in normal computers, not one that could hypothetically be good if it was used in them instead.

You can build a low volume ARM desktop motherboard if you want but it'll be just as overpriced, buggy and unsupported as any of the PPC attempts of the past 20 years.