My understanding is that DeWalt owns the patent on the "battery powered radio that's also a battery charger". I know that Bosch's radio also charges batteries, but my understanding is that they pay something like a $20 royalty to DeWalt for every radio they sell. Apparently that patent will be expiring in the next year or two, so be prepared for a raft of updated radio/charger units at that time.
I REALLY don't mind that my Makita LXT radio doesn't charge my batteries. My thinking is this: I want a cordless, battery-operated radio that I can haul all around a customer's home without being tethered to an outlet, or having to decide whether to charge a battery or carry my tunes with me. Besides, I can use my LXT impact driver daily and still only charge my batteries maybe once or twice a week. And when I do charge them, I stick the charger way off in a corner somewhere so it's not in danger of one of my coworkers damaging it.
I suppose one option would be to stick my radio in a Sys 4 or 5, drill holes in the sides for the music to come out?... But yeah, you don't need a huge radio, the BMR100W sounds GREAT and is approx half the size of my old Milwaukee radio. A Sys 1 or Sys 2 -sized Festool radio would be plenty, particularly for inside, shop use