I like this idea of Other Fruit Pi boards designed for special, non-general computing applications like routers. Is the stock pi design "open" enough that skilled board designers can just plug-and-play and manufacture these kinds of custom boards, or does it take SeriousBusiness™ resources to do these things?

I'd be super interested in a Pi with a few SDRs built in. Currently I currently play with a Pi with a bunch of USB SDR dongles jammed into it but wouldn't it be nice to have all the RF hardware and connectors built into the main board?