Battlegrounds are fine. They just need to treat the groups of them as one strike so you're not 3x as likely to get a heist battleground as you are to get a classic strike. Alternatively, they can select the best battleground of each type and just put that in the playlist so the odds aren't so tilted in their favor. In either case, all strikes should be unvaulted. If it wasn't an issue that cayde could narrate exodus crash after forsaken, it isn't an issue that the planets vaulted strikes took place on are gone. I like strange terrain, savathuns song, and festering core.