Navaids are easy to add, as you found out. Just code the XML, compile and you're good to go. You do have to watch for conflicting frequencies.
Since the MABs are going to be static, you'll be able to set up ILS approaches, position NDBs at whatever distance you want them to be read, even approaches, if you're so inclined. You'll need an airport file for each, which begs for an ICAO code. There are no airports that begin with MAB, so you could call them MAB1, MAB2, etc. Or... there are no airports that begin with PRK, so PRK1 or PRKA could be a format. And PIG is available, also! :salute: