As far as weapon options on basic troops the structure of most armies and the weapon rules in Gates of Antares supports a "small arms" list of a carbine, a rifle, a shotgun, and pistol/CCW; the Guard are certainly no exception. I'm probably not putting a long-las in as a small arms option, however, because the ten-guys-with-ten-sniper-rifles model GW uses for scouts/rangers/ratlings/etc. seems very antithetical to what a "sniper" is.
Actually, I'd prefer long-las to be like the stalker bolt rifle, a heavy lasgun with 12" extra range, than something with the 'sniper' rule.