If we're going to address specifics with a goal of improvement, we need to get the details right.
• The trunk is NOT disproportionately small nor shallow. The trunk cavity is sized very appropriately for the size of the car. What IS an issue for some owners is the trunk opening, which due to the tapered roofline, is relatively small. This only affects large, rigid items, tho I note that my son's 2x12 combo amp (22"x27"x11") slides right in (along with 2 hard-cased guitars and other gear). If you are trying to put something larger in, perhaps you need a larger car. But trunk volume is quite respectable.
• Headroom is fine for me & we're the same height.
• wife is 5'3"- she has no complaints about the beltline whatsoever. "Catastrophically" is without question an overstatement... unless perhaps you were talking about people 5'0" and shorter.
The trunk opening is a valid complaint (again- depends on what you're normally packing), and another is the rearward / 3/4-rear visibility. Sailing C-pillars are the culprit there- price paid for style. I personally would like the car to be AT LEAST 3" wider, but that's also not a 'catastrophic' situation.
For the record the Cruze and Malibu have the same trunk volume... Cruze has gooseneck hinges though.