By my point count, going from memory at work
it would be about 1600 for;
HQ: Commander, las, chimera
T: lt. Pwr fist. 4 flamers. chimera
-Platoon with missile / Grenade Launcher in chimera
-Platoon with missile in chimera
T: lt. Pwr fist. 4 flamers. chimera
-Platoon with missile / Grenade Launcher in chimera
-Platoon with missile / melta in chimera
T: vet with 2 melta. Missile Launcher. Chimera
H:Deathstrike with cammo netting
H:Deathstrike with cammo netting
H:Deathstrike with cammo netting
then you could adapt from there say 1750 throw in a devil dog or vendetta and upgrade some of the special or heavy weapons. Maybe a techpriest or two to sandwich in the back. For higher points a big blob of consripts with a commisar attached running forward to delay / block units would be good as well.
I would use the vets and extra tank to take care of anything getting close to the launch zone or at least tie units up so the launch continues!