MGO's weapon system is like CS I think. After a round you get points based on how good you played, with those points you can buy better weapons between rounds, or after you die, oh and during play you can just go back to your team's square zone to buy the new weapon and restock on throwaway weapons (traps, grenades, etc). There is a possibility more weapons will be added in time. Konami added a few new things recently but for the JP side so far. NA will get the update later.
Instructor skill (obtained by training newbs in the training mode that's currently available but no reward for training people until this is out.
When it come out I'll try my best to unlock this. I want to intimidate people and have a edge on people in this way. "Soldier! Get over here, and look at my pron traps!"
Also abou your question earlier. The pistol, sub machine guns, shotguns, sniper rifles, assault rifles, blades, hand to hand fighting, and pretty much every form of offensive ability (throwing distance, trap laying, and such) has a specific skill you can level up. But it also require slots, and picking which skills you want, to use, and which ones you want to start leveling to master rank is what defines the type of role you would most likely play for the team. I'm a type of demolition expert. I don't knock down doors with explosives, but I can blow crap up. I just choose to use pron books because it's funny, and let's me get easy headshots if I trap some people. I'm able to trick people into chasing me and lead them straight into a trap. Funny stuff.
Oh and this is a 3rd person game. Not everyone like that.