Wheels within Wheels

At this point I have a few ideas for how to handle goals and xp/leveling, but that still leaves the question of ways to engage the PCs. I don't want a higher level campaign that's just about killing bigger monsters. I want the players to explore some of the things that are unique to more experienced characters. Specifically, strongholds, domains, political/military conflict, and magical research/rituals.

Strongholds are –in many ways– the simplest of the bunch. A player character selects the site, pays the costs, and waits for construction to finish. The challenges here I see as twofold:

1. The "primary" PC is paying attention to things like layout and design and paying for it all.
2. The "secondary" PCs need to worry about things like keeping supply lines open, wiping out monsters that threaten the builders, etc.

Lots of adventure material there, IMO. 

Domains are more for after the stronghold is done, but players need to start thinking about them even before the first brick is laid. I also use "domain" as a catch all for other name level pursuits including thieves' guilds or position within a temple hierarchy. For wizards, it's more likely about figuring out getting supplies for one's tower, as most farmers won't live in the shadow of such sorcerous places. 

Military conflicts are more likely to be tied to larger events in the campaign than player-driven. Of course, ambitious PCs might instigate a border war with their neighbors. These can also be smaller scale skirmishes or turf wars between thieves. Political conflict could be court intrigue, a diplomatic mission, or a machiavellian power struggle within a guild or church. I can easily foresee external plot hooks as well as player-driven cases of these. 

Magical story arcs might stem from wizards researching new spells, priests performing ancient rituals, or the enchanting of items. The Adventurer, Conquerer, King system includes a lot of rules for these, as well as things like crossbreeding monsters (Bugbatbears, anyone?). Secondaries keeping interlopers away as their sorcerer boss is trying to complete a powerful ritual that will create an iron golem sentinel for the tower is worth a session or two I think. 

In addition to all this, I need to lay out some ideas about what might be going on in the larger world that can drive events in the campaign. Wars, evil gods, rampaging demons, who knows?