[PvK]

Seems to me that the admin rating could be used to re-balance forts. Gold cost gets repaid by admin, especially if/when you have the time and willpower to invest in building them, and choosing good spots for them.

The weakest forts don't provide wall defenders or bottlenecks. This could also be developed a bit - it could be interesting if some fort types had multiple breakthrough points during storming.

Some modding might help this by giving crappy low-admin little-value forts to unthematic choices, so building forts out of your nation's element is more expensive, time-consuming and/or provides little value, to a greater degree than currently. I.e. maybe the problem isn't so much that Mountain Citadel sucks, as that the nations which have it thematically, have better alternatives in unthematic terrain. With mod commands, they could be given alternatives of questionable value in unthematic terrain, encouraging more use of thematically appropriate forts and locations.