1 Russ upgraded to demolisher and given hull heavy bolter and plasma cannon= points saved from not taking regimental standard
This leaves 12 points to be invested 1 extra plasma in one of the command squads
I'd prefer the lascannon over the heavy bolter (can't move-and-fire with much, but it's a nasty AP2 deathtrap). At least use some magnets, and you can swap out sponsons/hull weapons as you experiment.
You might also play around with a 3 or 4-flamer platoon command squad sometime; you'd be surprised how many marines you can kill, when you don't have to roll to hit, and can hit 4 or 5 of them 4 times each.
Now to figure out how to model veterans, light infantry and drop troops.
Veterans: (my approach) they have more character than your typical guardsmen, as they've been doing this longer. Dirty uniforms, non-standard patches, personalized weapons (barrel length, wrappings, customized stocks, etc.), toothbrush or cards stuck in the helmet band, things like that.
Light Infantry: some camo netting, branches/leaves stuck on here and there, painted up in a camo scheme that matches their base?
Drop Troops: build yourself a movement "tray" for your dropping guys. Litter it with parachute (gravchute) remains. When they land, just put the tray on the table. For your small veteran squads, you only need a "tray" the size of the small blast marker; you may want one or two larger templates as well, in case you ever want to drop a full squad.