Was pondering the idea of autocannons too. We do have APCs and what seems to be the Cataclysm future equivalent to IFVs, though the only apparent difference is charging stations for whatever futuristic gear would have rechargeable mods installed. I should test whether you can mod the UPS to be rechargeable…
I also need to test whether vanilla vehicles can be overridden, then I could adapt the mechanized infantry carriers to have a few extra differences compared to the standard APC.
As for NPCs, hell yes. If I could get them to man the main gun. That, along with holding onto extra ammo and handing it over when I run low, will likely be a pipe dream.
And…which build? Ah, let’s see. As far back as…um…whenever they added the mounted versions of the M240 and M60, and/or whenever treads, shock absorbers, and rebar armor to Blazemod.
EDIT: This update to the main version likely marks the farthest back the mod SHOULD be compatable: https://github.com/CleverRaven/Cataclysm-DDA/commit/3acd006cf0bb05e79410bcede3a314699dc58707