At the moment, I'm enamored of VTOL artillery (like this). That's about 1/3 the price and moves 7/11. It's obviously much less survivable in direct fire combat, but for indirect fire and the ability to escape overrun it seems pretty good. Is direct fire usage worth tripling the cost?... maybe. Direct fire artillery certainly counters some units (infantry, speedsters, airborne) pretty hard.
A few other thoughts:
(a) I'm not sure the jump is worthwhile on an artillery unit. Jump + direct fire penalty puts you at an 11 to hit on a base of 4. That's a harsh diet.
(b) 4/6 seems a bit slow. 5/8 would let you avoid overrun from heavies. That costs 4 tons though which is tricky to free up.
(c) A Sniper fits nicely on an assault mech.
Honestly I didn't know VTOLs could fire artillery stuff when airborne, I had thought they had to land first. Not sure where I heard it from.
But yeah, the jets are basically there to keep up with other 'Mech formations that may also have jump jets, to cross ravines or something, maybe to relocate after firing to help evade counter-battery. They're not really intended to actually fire the artillery piece while jumping. I guess there's enough ammo to waste on it, though...
4/6 seems like the practical limit for a 3025-style Thumper platform, even without the Jump Jets (you can do it but you lose a lot of armor in the process). Endo-Steel access makes 5/8 practical even with a regular fusion engine, which makes it fairly cheap. In that case I'd go with a 60-tonner, because you can use the ubiquitous 300 Vlar engine.
Snipers fit on Assault 'Mechs, but I think I prefer it on heavies. If I can stop playing Helldivers long enough to finish my Mechani Alliance 'Mech writeups, one of those is a 4/6 75-ton Sniper platform. It's pretty effective.
