Full weapon customization is something that every shooter should have by default. I don't like that you have to reach a certain level to get a certain weapon at all, games were fine in the past without "unlocks". The only thing that should be locked is progression points like what Americas Army had on the xbox.
Maybe unlock different types of scopes, ammo types, gear but not weapons. Ranks should also be locked but real military style ranks should be included in every military shooter , along with a proper Unit system for fireteams, squads, platoons and companies similar to what SOCOM: Confrontation had.