I'm not excluding the possibility of someone getting creative and offering a reasonable answer to those.
I mean, heck, the game used to run: 1 city/stronghold, 1 duchy, and those titles WERE tied together. Reverting to that would fix a lot of these issues if not all of them, though could certainly feel like a step back for many.
Adding ducal seats as optional, so that some duchies with cities offer local recruitment while the rest centralize it in the realm's capital, would probably be a much better fit, and would also address a lot of these issues.
Because I don't think we should start allowing recruitment in non-city/strongholds. I also don't think any given RC should make troops available at more than one location (probably easier to manage at duchy level than RC level), to make sure that decentralization has a proper cost. But I also do like the general idea of greater decentralization, so that a lot of currently non-viable realms could simply be annexed into larger realms where they would be exposed to more other players to collaborate with, and that successful and dynamic realms are not stopped dead in their tracks by mere distance issues. Realms have few enough neighbors as it is and we've greatly incentivized super-realms over the years, which was fine when stale super realms would snuff out dynamic smaller realms, but it increasingly feels like dynamic realms are being mechanically held back into staleness while less successful stale realms enforce their stale status quo.
If realms could expand, and expand, and expand, well, then maybe the stronger realms would do so, and we'd finally see more wars, more border changes, and eventually new blocs rise to oppose them. On Dwi, this could mean: Astrum would have more ability to project some power in the east and in the west simultaneously. Swordfell for north towards Astrum, Morek, and HD and south towards D'Hara and Luria, D'Hara towards east and west, Luria towards north, west, and south, etc. It would mostly mean more realms would have more options and more capacities to do more stuff. And this is better than everyone being holed up.
