I found this thread Friday when I found out my downstairs bath has a 10" rough-in.
I was pretty upset because my new Toto Drake 744SG wouldn't fit. (Luckily my upstairs bath has a 12" rough-in and an Eljer that needs to go as well.)
I had decided to go with a Mansfield pressure assisted model, so I checked to find a local dealer. The local dealer here for Mansfield is also a Toto dealer. When I called to see if they had a unit in stock that I could pick up they told me I should get one of the Toto units they had in stock.
Well, I had looked at the retail Toto units that would fit a 10" and came to the same conclusion as you, but here is what I bought.
Toto CST704.10B
This toilet is from the Toto commercial line, and was indeed what I wanted. The CST703 model was rated on a lab testing pdf I picked up somewhere @ >500 gram flush.
Although I have only had it installed for less than 2 days, my daughter managed to clog it. Turns out she flushed paper towels
One quick plunge and they were gone.
Tommorrow I will install my Drake upstairs.