3 major points, though I don't have the ideal solutions:
1) Lower the incentive for camping castles. The ideas people are coming up with for tactical advantages / points of interest is a good thought. Better functioning siege equipment and adding versatility to gaining entry would add tons more to strat.
2) Field battles / construction / spawn points should be reassessed. Attackers need to run half a mile to attempt to make forward spawns, while defenders magically summon a siege tower from bits of wood they held in their pockets. These couch fortresses of forward spawns covered in vertical ladders is just plain silly because it encourages long, drawn-out battles where 2-3 agi builds suicide in and harass the extremely brittle, but extremely necessary forward spawn. The time limits, though necessary, don't add to the game at all when battles turn out like this because attackers literally can't do anything with a limited roster to keep their push going. Closer spawns might be all it takes.
3) Limit the micromanagement involved with gear and economy. There must be some way to simplify outfitting armies. Also, as far as economy goes, it might be beneficial to allow fief owners the ability to automate some things. Boycotting undesirable merchants and allowing mutual trade agreements could help smaller factions, especially those who don't have the time to check the strat map at 5 am and monitor S&D.