I think it could be a very good target for a Rockbox port, however they very specifically emphasize Lua and hackability among their goals (check out the UI code

I think it could be a very good target for a Rockbox port, however they very specifically emphasize Lua and hackability among their goals (check out the UI code samples); they're also developing the hardware+software platforms in tandem, I'm not even sure if Rockbox supports Wifi or BT.