I noticed early on that I couldn't kill the green AI that starts south of me. If I kill all their scouts, they magically respawn with 4 units.

So I figured out an exploit. I kill all of their scouts except 1, corner it somewhere, and then build an outpost on that territory. 

They lack the combat strength to fight their way out, so they just sit there. They can't start an outpost on that location because I own the land. So they just sit there. 

I leave them there until I get to Medieval times or so, then I let them go. They have to travel through my then-extensive empire and settle in between me and my enemies, which is convenient.

Can you just let me kill them off early instead of having to exploit them?