As much as I like Medusas I would consider some other form of Artillery to add to the mix. You have nothing with a range longer than 36" (except the RR's which are easily taken care of) so all someone needs is to field longer ranges stuff than you and pound you to hunks of meat.
Been direct fire only the Medusas are within sight of the enemy's AT weapons, so another reason a mix of Arty would be beneficial, preferably indirect fire ones...still stays within theme.
I agree with the others...great theme, but CCS and Infantry units without SW/HW's is missing a trick = much needed firepower. A Commissar - led combined Platoon is also a very good way to increase their weaponry's efficiency and staying power...also helps protect your Artillery.