I thinking adding the feature like Live TV Streaming/DVR for radio channels would be really nice feature to have.
Like how some programs on live TV lets us discover latest trends, the songs/programs on radio [AM/FM/HDRadio] are also interesting bits to be used.
There are many open source options which decode the signals digitally, all we need is integration with Plex.
I suppose what you’re looking for is already covered in an existing feature suggestion. If so, please comment/vote in that existing thread in order to avoid distracting/dispersing votes.