Not seeing much point to an artillery mech that can't jump. To really justify being a mech not a vehicle even the Helepolis is a bit of a slug. It can get up some cliffs and over some ravines an SPG can't and you can put it in an orbital drop pod, but it's not going to keep pace with anything but an assault mech in strategic ground movement.
Even in the succession wars you can get a Thumper to 4/6/4 which will at least let it keep pace with Partisans on roads or your standard line of battle mechs off-road. The easiest way to do this is to swap out the AC-20 on a Victor, which shouldn't be an assault mech, but is for no good reason so there's your assault mech artillery. Someone's probably going to try to copy the Harquebusier's all terrain artillery this way.
With the tech Catachan has you can do 5/8/5 easy. Well, easy as balancing the jumpjets on something with a quarter of its mass tied up in a gun in one arm. You need an XL300, which they've got, DHS, which they've got, and probably want endosteel to fit reasonably threatening secondary weapons, which they've got. And getting an overhead track built that can handle a 60 ton mech in Catachan gravity. That's going to be a lot less of a stretch than one for a 95 ton Banshee. It's only 9% more than the Hoplite line rather than 73% more.