[Guitardian]

This has never come up since I have not played a lot of games, but I was looking at my chimera with its back hatch that can fire a weapon from the squad inside and wondering: if i built on some kind of cupola turret to accomodate the squad gunner over that hatch, would that let me use the 'armored crew compartment' upgrade in the codex and fire without becoming open-topped for a turn?

[Wargamer]

No.

[Go Guard Or Go Home]

Armoured Crew Compartments can only be applied to a "opened top vehicle" since a Chimera is not designated as an open topped vehicle you can not take this upgrade.

The fact that you can open the hatch and fire a weapon does not change the designation of the Chimera on a permanent basis it only counts as open topped until the start of your next turn. It does not become an open topped vehicle.