And I've received a helpful anonymous comment on my first Green Saree Regency plan, explaining that these diamond-back dresses usually closed in front (as I suspected).
Inspired by that comment, the neckline above and all the round gowns I've seen, like the Met one featured in that preceding post, I drew another sketch.
The neckline is higher than usual. I stick to that. Boatneck necklines suit me.
But the drop-front should make it easier to put on by myself.
I still have to figure out what's going on at the "waist", but that's a minor obstacle now that I've settled on a style. :-)