Hey guys, stop it, let's get back to the topic (and I thought it's gonna be closed for being request, well...).
As I firstly noted: MMO style game with 24h server can be ruled out - no JIP, and nobody gonna fund us a server. Albeit, traffic would be very low. But, it is possible to make RPG-style campaign with full story and stats and equipment that is saved between missions, just look for Zeewolf or Faguss experiments. But I'm not sure if some scripts, simulating survival aspect of the mod, won't make trouble in MP. I can bet that such mod (even in SP) would be laggy too - some scripts seem to be "always on", like exhaustion system, or eating system. They need to "observe" player/NPCs condition all the time and decide if it's time to say bye bye or not OFP engine limitations can cause problems here (memory managing).
Unfortunately my scripting knowledge is very limited so I'm not sure if I'm right, but it doesn't look hard to implement at least part of DayZ features into OFP mod.