i second the recomendation for the brothers in arms series. very good story, more emotional than any other fps out there, and the fact the maps are based on actual research makes it better.. hmm i wonder how a campaign based on it and the actual real events would go. the adventures of red and bullet proof matt baker.. although the latest one adds tank driving sections which is mmm very arcadey to say the least.
i cant remember the name of it but i distinctly remember a game from a few years ago where you ended up with letters home to the families. it was a very sobering moment.
the mockumentary "tales of virtual combat" shows what can be done as well with just a little creativity.
one idea i had. some seperate files with each campaign. password protected and you get the password in a briefing or debriefing after or before a battle. things like letters from home, maps, a photo from a loved one. more detailed intelligence reports and for someone creative. maybe a short movie or two