Some arm sbc computers have schematics available. Could someone with equipment for bga components and a means of making pcbs theoretically make a backdoorless one and use it to do all the illegal stuff they want?
There are open source x86s now but homebrewers are just now getting around to making barely working, not even good 386 and 486 stuff so it'll be a long ass time before open source x86 stuff becomes more viable.