In Roller Coaster Tycoon 3 it seems as if the game encourages you to fire senior staff members and hire junior ones instead (it's cheaper than educating them). I would like to see a more sophisticated hiring and firing system, so it wouldn't be best to fire senior staff all the time. Maybe staff can build up experience and do things quicker or better (alongside an education system). In that case hiring a junior member instead of keeping an experienced senior staff member would reflect real life: senior staff maybe more expensive, but they have the tendency of doing their job better and/or faster because of their experience.