Question about usage of window margin flavors

[Richard M. Stallman <RMS at MIT-OZ>]

How many of you use the flavors 
BORDERS-MIXIN, ESSENTIAL-LABEL-MIXIN, BASIC-SCROLL-BAR
or MARGIN-REGION-MIXIN directly in your own code?

Anyone who uses the flavor WINDOW is using some of these
indirectly, but what I am asking is whether you actually have
those names appearing in definitions of your own window flavors.

I am considering an incompatible change to the way these flavors
interact with each other, to simplify it, which would require
trivial but incompatible changes every place they are DIRECTLY used,
and I want to find out how much this would impact the users.