I dont know if you guys have contemplated this, but are you interested in putting in a npc or group of npcs that players can pay to follow them or maybe to perform an action such as hold the keep or follow them or hold this, such as in skyrim but on a bigger scale. I think that it would be great to have a set of troops assigned to you based on your rank and you have the ability to share control of them. So that players dont always have to be online to hold a certain keep. I know there are many other places you can go with this, but the biggest problem I have with WoW world pvp is that if your faction svcks, you will never win or even hold the base for long. Maybe this is a way to offset that? perhaps as you rank up in the pvp rankings you attain certain military ranks and the higher up you are the more soldiers you can control on the battlefield.

as far as i know, when your faction takes over a castle there'll be NPC soldiers you can train and stuff. i think there is already something like you descripbe in the first sentences :] im not sure if you can basicly move them from one castle to another tho..
or if you're able to 'restock' soldiers?! xD

When you took over a keep in DAoC your npc's would start to spawn in it instead of the enemy ones, they did not appear all at once though and it took some time so you had to hang around for a bit and make sure enough NPC's had spawned.