In codex space marines Stern Guard veterans are allowed to take 2x additional lascannons for 20 points
making the unit cost a total of 145 points. If a player takes Pedro Kantor the stern guard can also be scoring. The stern guard have +1 leadership and attacks over standard marines but I know that would matter very much with a support unit.
A devastator squad would cost 160 points if it included two additional lascannons. I know the devastator squad also comes with a signum boosting one models BS up to 5 and that would give the devastators a advantage over the stern guard of course.
A Stern guard squad with two heavy bolters or missile launchers would cost 135 points and three members would still benefit from their special ammunition which would be great for anti-infantry. A devastator squad would be cheaper at 120 but without special ammunition I don't see it packing quite as much punch.
My question is has anyone ever tried taking stern guard with heavy weapons in place of devastator squads?
Or is this idea a really stupid one that should never be attempted?