Forgive my vagueness, but in earlier days, there was talk of the game's 'higher levels' (6th and up at the time) involving Keep building and more of an Empire building/maintaining vibe. This was moved beyond the main rulebook when fan-pressure pushed the range of levels up to 10, and may still be on the drawing board for a future suppliment to DCC RPG.
They're called Domain levels in OSR speak. ACKS has some good stuff that focuses on Domain levels. Domain levels would probably start at 6th in DCC as opposed to 9th in most other games. But DCC RPG is focused on adventuring and crazy magic, and not Strongholds and Domains.
I don't think Joseph isn't particularly interested in that type of gaming, and personally I feel the same way. But I did pick up ACKS for reference if it comes to it. Swords & Wizardry, my go-to game for rules & what-not that's not included in DCC RPG, has some stuff to, but not nearly as comprehensive as ACKS.
Since both of those games are OGL, hacking them to fit DCC RPG wouldn't be very hard and legal to do so. I'd be curious to see what people would do.