Or, maybe you could lose food or gain a new alchemy plant (maybe make an alchemy 'garden' for this idea in VV4?), etc. besides or instead of new villagers.
"Gifts" (or bribes) for the other village to send recruits? I think that's a cool idea. Or maybe you sacrifice one of your own villagers in a trade with the other village? Like one Adept for two Trainees. Or something. TWO with fresh DNA!
I've heard of many villages in some third-world country who--every third or fourth generation--send some of their people to neighboring villages for this very purpose. To thin out the gene pool. This would be a good way to interconnect the villages of VV1, VV2, VV3 and VV4.