Quoting myself.

Quote - But I wonder if the forced limits are impacting on how the feet intersect with the ground in the WD?

I don't think so. The Walk Designer seems to use some sort of "Drop to Floor" for the feet, so the foots altitude should not be a problem. Am less sure about the bend angle. On the other hand, the distance between the hip and foot affects how, and how much the legs bend. But perhaps I should stop speculating and do some tests. Things have been moving so fast lately, that speculation is all I have had time for.

Q: "Do the limits work when the user has "Use Limits" off?"

A: Yes.

Quote: I could see potential for translation problems with the Walk Designer, if limits are forced.  If the WD is going to translate the actor named "Hip", using limits might cause it to leave out all translation, which could be bad all over.

Yes. :(

On the other hand leaving the limits unforced has implications for applying stock poses, unless some action is taken to transfer translations applied to Hip over to Waist, as you suggest.

For stock poses, and the WD, it seems that transferring the translations and rotations would be desirable. But would this be desirable for manual posing, and what impact might this have for saving poses? I don't know.

I did try transferring rotations from the hip (former hip2) to the waist, using ERC. Unfortunately I ran into problems. yRotating the hip caused distortions in the mesh if the rotation exceeded 70°. There were also problems with xrot and zrot. Perhaps this will work better if implemented through Python.