We should probably mention the Nova, Hunter and Gladius, even if we agree they should remain unchanged.
Nova: for +15pts over the Firestorm you get +10cm speed, F/L/R Lance (the lack of which being the main flaw of the firestorm), and Space Marine Rules. In addition, it's meant to be difficult for SMs to get lances. I think that probably doesn't need to change, even though it's the most expensive Imperial escort. Possibly 5pt reduction to 45pts?
Gladius: for +10pts over the Sword, you get +5cm speed and Space Marine rules. Worth the whole 10pts? Perhaps 5pt reduction to 40pts?
Hunter: for +10pts over the Cobra, you get 5cm speed, 5+ armour, and Space marine Rules. I think that's probably worth 10pts, so no change.