This ladybug obligingly held still while I took a stack of focus bracketed images at, apparently, ƒ/3.2 and 1/100 sec according to the EXIF data. (Don't look at me, I was in Fv mode.) This is hand held, and it's always equal parts pleasing and mildly suspicious how well Helicon manages to line all the images up afterwards.
Bonus homework:
I'd doubt that would work. You'd also be changing the distance to the subject, and in so doing changing its size in the frame each shot.
You could probably do a burst and twist your focus ring manually throughout, though.
Sounds like an interesting after work test! You've got me very curious. If I'm doing this hand held there will likely be some wind, so things are going to move a tiny bit naturally. That and most of my lenses exhibiting focus breathing, so even if the camera were stationary the perspective would change slightly.
I'll hopefully follow up soon.
For science!