The only heavy weapon with 3 arms is the mining laser, having versions of the stubber & seismic cannon would be nice. Since the Acolyte hybrids (especially the 1st gen ones) can take a wider selection of weapons it’d be great to have those options (With a few variations of each ideally) - from a simple long las for the more human acolyte, to basic, special weapons, and cc weapons for the 1st gen acolyte: A 1st gen acolyte can now totally wield a grenade launcher, power maul, and 3rd arm for instance. Some extra backpacks with weapons / kit similar to the existing ones used on the Neophyte heavy weapon models might also be a nice touch.
Basically there are a lot of fun new options which the current kits don’t really support. Now that I think of it, there was that gunslinger character which was teased a month or so ago... it felt a bit more Necromunda like than 40k