Here's what I think could be done

1) build lvl1 NPCs all around you within 20mile radius(make all resource slots farms)
2) tear down all other NPCs
3) store your resources on the market
4) keep your gold on the move
5) every time you see a train of attacks to lower loyalty. Hit the low-troop ones with 30k archers.
6) with another 500k pike hit any cataphrat armies less than 200k.
7) keep your troops on the move9(farm those lvl1 npcs for food)
8) pray your way incase loyalty gets low( if you have all tech's maxed out, you should have some spare gold). If not use blessing or whatever its called.
9) ask to see if you can join their alliance or sister alliance (after all killing you might not be worth the trouble)
10) if they go an capture one of your lvl1 NPCs and grow it up, teleport. If they are gonna put that much effort into taking your one city down, you probably did something to deserve it.

Thats just my opinion.