[Psitticine]

I rather like the chance-to-retreat option. Possibly a chance based on their Sneak level and general experience level to get away? Also possibly modified by the local defense and patrollers present in the province targetted to retreat into?

I think if it isn't automatic, that would keep it from being overpowering, and it makes a lot of sense for stealth units to "retreat into the shadows" if they are lucky. After all, hiding is what they do!