I think there's no reason to make a separate chassis for a different CPU architecture. Most likely it'll be available as a new motherboard.
As for a complications I'd say it's kinda not clear whether it'll be possible to swap components on the motherboard and boot any OS that has been compiled for this CPU architecture (like currently with PCs). Current devices that have ARM CPUs (smartphones and other single board computers like Raspbery Pi) require OS that has been built for that specific phone/board and additionally I haven't seen any ARM board with replaceable RAM.
I think there's no reason to make a separate chassis for a different CPU architecture. Most likely it'll be available as a new motherboard.
As for a complications I'd say it's kinda not clear whether it'll be possible to swap components on the motherboard and boot any OS that has been compiled for this CPU architecture (like currently with PCs). Current devices that have ARM CPUs (smartphones and other single board computers like Raspbery Pi) require OS that has been built for that specific phone/board and additionally I haven't seen any ARM board with replaceable RAM.