I think a ranking system the way described, unlocking classes and such is a bad idea.. Which is why i'm voting no. The reason for this is that it is a sandbox game, and a MILSIM..
A game like this should at all times be based on skills, and not on how high a rank you have.. Which weapons you get, is decided by the mission creators, and that is what makes a great game with equality..
Clans even use this system to set up their own big fights that may last for 30 mins - several days.. Being able to actually set up a fully functional army unit, if there is enough members.. So instead of being just a shooter, this is an opportunity to experience army life without the fatal consequences.