An interesting read.
Communicating thoughts in this way is what we have raised together on this forum and Kudos for taking that on board, its noted and appreciated.
My only concern arising from what i see is anything that resembles the old back door hokey kokey as that was the worst mechanic ever to be brought to the moors.
I mean its tricky, but any situation where we create a jump inside in combat, jump outside in combat scenario with defenders using (abusing) this mechanic is depressing to even think of.
Hard to see how else it can be done if you are closing the main gate and people still need to get inside and outside;
or are you suggesting that folks can leave, but to get back in they have to have the npc out of combat? That would make it hard for strays to get into the keep when its under attack, but would prevent the old back door horror we came to hate so much.