I usually use an Echo 1 G36C as my primary with a green-gas M1911 as my secondary. I also have a sling on it so I don't have to carry it during long ops and a front grip for CQB. Honestly, the G36C is a fantastic gun when it comes to airsoft. Good distance, good accuracy, good RoF and a stock that you can fold in for CQB. Slap a hi-cap on that baby and you're good for whatever comes your way. Even my stock version of it's able to outperform alot of these expensive customized guns.
As far as optics go - don't use them unless you're rolling with a sniper rifle. It might look cool, but ironsights will work just about as well. Protip: Don't bring any more gear than you need. It might seem like a good idea to bring 5 guns, but after half a day of lugging around 50lbs of gear you'll wish you'd just left them behind. That's why I usually only use the essentials. Rifle, handgun, face/eye protection, wool-knit cap to protect my scalp, gloves for grip/to protect my knuckles, a t-shirt, shorts/jeans (depending on where the op is), sneakers/boots (again, depending on location), some extra ammo, water, and maybe a radio if we're going to need to split into two squads. No need for BDUs or vests or any of that crap. Rambo-esque headband optional.
And if you do end up getting that L96 remember not to shoot anyone that's too close to you, even if it means dieing. A 500fps gun can lodge a BB in underneath someone's skin and it's a serious pain trying to dig that sucker out. So use your secondary instead.