I will use the ship, or a blaze shot or two from a bit of range doesn't trigger a response. The I use the scatter up close.
the jet pack upgrades are all a bit small individually. I have 11 I think. There is the jetpack itself, and 4 buildable upgrades, then 3 s mods in inventory, and 3 s mods in the tech slots. It is a significant difference when they are all together. I also use a little trick that changed the game for me. I bound my melee key, Q by default, to a comfortable mouse key. Sprint ( W+shift) then while sprinting hit the melee then space bar. If you activate the jetpack while in a mid punch sprint, you shoot across the landscape. Take care doing this off a hill though. I have almost killed myself a few times falling.