Anonymous Ringer: Averted with the Chechnya and Taliban factions.
A.K.A.-47: Averted for the most part, though the "M16A2" used by the Hamas faction is really an M16A1 with a different handguard.
Hence why they're working on the ARMA version and are ultimately pushing towards a stand-alone Project Reality 2, which became Squad. And those that do exist are often the result of the Battlefield 2 engine's limitations rather than the developers' own intentions.
Acceptable Breaks from Reality: Tried to avert as much as possible.
Project Reality provides examples of the following tropes: