for making units unrecuitable but replenishable

[Pannonian]

I have seen this question pop up a few times and so i'm gonna post this in case anyone still hasn't found a good answer.

I've found the best answer is to make the unit's build time something ridiculous like 800 turns. THat' way it's still retainable.

Surf

I think it's possible to replenish but not build by adding the unit to buildings.txt but not units.txt. I'm not sure though if it's possible to have multiple instances of a unit in buildings.txt without it ctding.