Ha ha! I actually found where a leg vise was installed on an Adjust-A-Bench. Benchcrafted's website and blog even point out that Jeff Miller is the one that asked for that ability, and perusing their Instagram history led me to this: https://www.instagram.com/p/B72VyZshSTJ/
Interesting, but like I noted before I'll probably want my assembly table to be height adjustable but not necessarily my main workbench.