[Edi]

Yes, there is that. The point is that you should not use enslavement against indies or you will suffer the consequences. I can't fix things perfectly. Using inflated resource costs causes the AI to still try to build them, stuffing up recruitment. Inflated gold cost makes them impossible to recruit, but if you hit one with an enslavement spell, you're suddenly paying 600 gold upkeep on that unit.

So, save enslavement against AI armies, they will only have the unmodded units in them.