I'm thinking of making the "kick out" penalty greater -- kicked out units get sent all the way back to their capital. That way, sneaking across someone's territory and getting caught is akin to being deported.
Please make the penalty greater, or different, but please reconsider the word "capital"...
Seems kind of an odd feature to boot back to the capital, since that will change over big maps or small maps, it will change whether im behind another player into a third players territory (prolly make me go to war instead) and its all dependant on where my capital is, I would rather see a "closest City", or "outside the borders, but stunned 1-2 turns".
It could also be that if they reenter your territory in the next 4 turns they will automatically declare war.
Also there should be some special action from the AI if I keep entering theyre territory...
As a side topic to how angry they get when i enter territories etc. I hope the AI's Diplomacy will be greatly advanced.