I know this is a tall order, but your excellent mod opens up the possibility for something I would like a lot: Make it possible to spend both time and money to train your kerbals. Right now the only way for them to become good at what they do is through sending them on missions, which kind of defeats the purpose of an astronaut training complex. Kerbals should be prepared to handel a lot of situations. Basically what I'm suggesting is that kerbals can be put into training(making them unavailable for missions), and after a certain time they get experience. The higher their level the more the training costs, and the longer it takes. Since they get paid more during training, the player has to decide whether he's willing to send green crew or cough up the money and invest the time to send kerbals out. I think It would be a good idea to set a cap for the amount of exp the kerbals can earn this way. Well, just thought I write this, I have no idea how hard it would be to implement it(I'm guessing hard, but your mod seems to go in that direction anyway), and I'm not the least bit qualified to do this myself.