General How do you feel about "Mercenary" units that anyone can hire?

I remembered how mercenary units used to cause serious issues amongst my friends during old RTS matches . One guy would suddenly hire one overpowered nonsense unit and destroy everybody’s hard work instantly. But honestly i still like the idea. It adds unpredictability to matches. The annoying part is when devs balance them badly. Mercenaries should support strategy, not become the whole strategy.

Mercenary units are fun until the developers get carried away. I like them because they create those unexpected moments everyone talks about after the match. The problem starts when the entire game revolves around rushing to hire one overpowered unit. Then that strategy disappears. A small amount makes everything better. If it's too much, you've ruined what was already working fine.