Allow spies to recharge stealth using leverage

Imagine sending a spy to an opposing country. The journey takes 12 turns. They get there, and immediately stumble on an enemy stealth unit, which removes all of their stealth. Now you need to send them back home (which takes another 12 turns) so they can recharge their stealth. 24 turns of pointlessness.

Instead, it would be better if you could spend the leverage you have against that culture to recharge the spy's stealth (like setting them up with a new cover story). Spies would be more useful and sending them on long missions would be a lot less frustrating.