As for rifles, I'd suggest one "classic" assault rifle, most likely 5.56 NATO or 4.7 caseless (if you wanna keep to "real" calibers), and battle/marksman rifle, 7.62 NATO cal, that would be stronger and more accurate, but slower (probably special mode 3 round burst aimed, to use over medium distances).
A few suggestions: early research project "Scraped Stuff", a revival of some old experimental weapons. For example, automatic anti-materiel rifle (would work like autocannon from old UFO,especially good for throwing some small explosives over large distances). Also, I'd like to see lateer ingame improvements to rocket launcher, I love the stuff for indirect fire, but later lacks in damage, and some mid-game sniper rifle (seriously...lasers phase out sniper rifle, and then you have nothing for sniper skill till coilgun).