i am bit scared of the developement of the salarys especially for the staff types with heavy demands like the level 5+ trainers.
You are right when you fire a staff member he went back on the market again, but actually he get gets a new random salary and i don't think that would work with your proposal because you need to get a loss in value over the time. So the question is, would you like to see the money drawn out of the system through salaries or signing fees.