In addition to being able to work in a space, also being able to deal with a wide array/vendor choice of possible thermal solutions, economically, to deal with

In addition to being able to work in a space, also being able to deal with a wide array/vendor choice of possible thermal solutions, economically, to deal with up to 200W TDP CPUs and high wattage GPUs in a relatively compact enclosure. I wouldn't want to go smaller than mid-tower ATX case if doing something like a really powerful single socket air cooled CPU and a serious gaming video card.