I did not go that crazy as you guys (because I'm a programmer and I want to keep the amount of work to a minimum :p)
I got the following in my mod design:
A soldiers hall of fame, with for each soldier the recruitment date, number of kills & missions, the KIA/MIA date, it's rank and 3 possible medals he/she earned.
The 3 medals an agent can earn are : Expert Marksman, Expert Explosives, Expert Medical.
Conditions for these medals are still to be confirmed.
On the soldier progression of stats: this is done while in combat, not at the debriefing and it is announced in the messages window.
( it's the idea of making the player more aware that bringing units into combat is a good thing for their stats. When he only sees this at debriefing he already forgot how he got those skill increases.)