Gas is not as bulky as ore or ice so there is no need for large mining ships like barges for it.
Venture does the job just fine, Prospect if you want to be sneaky.
I’d rather Prospect lose a low slot for an extra utility high, so it can fit probe launcher, cloak and have 2 gas huffers at same time. Or give it Endurance treatment: triple ore&gas harvesting Role bonus (from +100% to +300% effectively doubling gas huffing yield per gas huffer) and lose one turret hardpoint. That will make it harvest gas clouds at same speed as it is now, but will free extra high.