[Suicide Junkie]

Ok, then.

The main idea is that lifesupport requirements are nearly flat-rate, and CQ goes up fast.

If you are focussed on the cost, and are not worried about taking damage and having the backup CQs work, then how about this:
Have two components. Crew Option A, and Crew Option B.
Use mounts to make these two options whatever size and cost is needed for each hull.
Players pick either A for your combo-LS/CQ, or B for the Divvied up LS/CQ