After skimming some equipment lists . . .
I think one of the cheaper ways to bring artillery in to BV limited games would be the Pollux ADA Heavy Tank (3/5) towing a ADA Gun Trailer (3/7), think cheaper Destrier, which gets your 30 shots (via 3t) with the Sniper and 30 A4 shots (via 6t) which can let you mix up the ammo load to provide sufficient options. The BV for this is 1414 with some variation if you bring Homing/Copperhead & TAG. For 4k, 5k or larger games its a tidy little damaging package that can follow your mechs forward.
Or for a bit larger, add 4 Snipers platoons as field guns with 3/8 skills, the BV total is 1982. Which is not bad for getting 10 shots with their load out.