Reconsidering
During the long "slumber" while I'd been unable to work on the house, I'd still given aspects of its design some long, hard thought. After all, I had a surfeit of time in which to make any number of tweaks, so I made the best of a bad situation.
Office Ceiling
The more I'd looked at the office ceiling, the less I was inclined to keep it that way. While I prefer low ceilings, this one is awkward because of how it meets the windowed wall: there is almost no space between the ceiling and the window openings (highlighted by the arrow, below), and I don't think this looks good. And I sure as hell wasn't going to make the windows smaller to compensate.
My initial thought was to raise most of the ceiling, leaving it lower only to enclose the air return duct, with a 45-degree slope connecting the two levels (in keeping with the visual style of the house). This would necessitate relocating the small heat duct to Kitty Central, as well as the gaggle of electric lines headed for the kitchen, as seen below.
An alternative to this approach would be to locate the height transition right over the windows, which would look sort of like an upside-down window well. I honestly don't know which of these I'd prefer, or if I'll just leave it the way it is and live with the awkwardly close window-ceiling corner.
Final verdict: I split the difference, and made an angled transition from low to high as close as I could to the air ducts and wiring without having to make any changes to them.
Closet/Laundry Ceiling
The closet/laundry ceiling is two levels, with one end lowered for the HVAC blower and access door (below). I'd thought about making it all one level, which would eliminate the hard vertical height transition in the middle of the space.
Lowering the high end would entail rebuilding the storage shelves over the entertainment center (below), which would be a royal PITA, as well as relocating four recessed lights.
Another option I'd considered is to reinstate the angled transition between ceiling heights I'd planned before I rebuilt the blower enclosure—I still had the angle-cut two-bys I'd made for it way back when. This would also require relocating two of the four recessed ceiling lights.
Final verdict: I left it just the way it was. After all, it's only a closet. Sometimes I really over-think stuff.