You have a great dress collection, Sally! I agree with all your reasons and observations about what makes a dress work-suitable, at least for your work setting.
I mainly work from home now, but I do teach in a classroom once a week for part of every year, usually fall or winter, with additional short classroom teaching gigs at various times of year. I also sometimes have to give presentations and sit on panels, or take on otherwise public-facing roles both in person and online.
I own almost no dresses, and those I own are all essentially summer dresses. (My entire collection, below) I don't think any of these would be inappropriate for a work environment (especially if I put a topper over the sleeveless ones) but I don't teach in the summer months, and even if I did, I probably wouldn't reach for these. I do wear skirts at work, though. So it could be that the only thing really holding me back from wearing a dress to teach in now is the fabrication of the dress (i.e. it needs to be warm enough.)
In general, I'd say for me to feel comfortable wearing a dress in a work setting, it would have to be covered enough (so no cleavage, not that I have any), not a lot of bare skin, period. Not too tight. Comfortable to move in (I have to move around a lot when I teach). Be wearable alone or with topper. Be wearable with low heels/ flats/ flatforms. Be easy to care for. And -- a more personal aspect, for me and my own style, I guess -- not feel too feminine. I probably wouldn't buy a dress that feels "too feminine" (whatever I mean by that), but if I did, I wouldn't want to wear it to work.