I know the Bolt Rifle and the Particle Beam Rifle have a sniper mode, but a new dedicated sniper rifle would be nice. Both sniper modes take up more TU's than the basic sniper rifle and have less range. Late game, I find the laser rifle pretty much obsoletes my snipers. I normally include 1-2 snipers per mission and they generally have great stats by the time I get to particle beam weapons. I'd feel bad about wasting them by retiring them and it takes too long to retrain them on other weapons.
So why don't I just give them particle beam rifles? Cuz i'm always low on ammo since my assault (4-5 per mission) troops are equipped with particle rifles. I know that sounds like a crap excuse but since you can't produce more particle ammo, I keep using the basic sniper rifle which becomes less and less effective.
A solution could be to have the Bolt Rifle research unlock the Bolt Sniper Rifle research. The rifle would use the same ammo, but do slightly more damage than the basic sniper rifle (120 for a snap shot) and have similar firing modes as the basic sniper rifle but use more TU's. Plus, this makes the bolt weapon research have more use since Bolt Rifles are kinda crap compared to the laser weapons.