I've pondered this occasionally, but it wouldn't work well IMHO. Despite the posturing of some gamers as being "hardcore" and only playing super mature titles, the reality is the majority of combat orientated gamers don't really want anything close to real combat.
Real combat involves a lot of waiting, a lot of tension and of course very real danger. Gamers want to win, even if they win by inches - i.e. on harder levels creep steadily through a campaign with perhaps many re-starts to press past one short sequence. Sure, some titles do try to re-create some elements more closely, but check points, saves, etc. and re-spawns are an every present rescue from danger.
Only a few titles I've played have close to real combat in any way, mainly PC titles in the past.
Mind you, playing devil's advocate, I notice hardcore in Dead Space 2 seems to have exerted a strange appeal, with it's limit of three saves to play through the whole title (4 on 360 I believe) start to finish... so who knows, maybe it could work if provided as an optional difficulty level.
Try to be reasonable... its easier than you think...
