On 03/07/2014 09:16, Joseph Wright wrote:
>   3. Are these more complex possibilities needed for \coffins_...?
>      (Currently there is only \coffin_resize:Nnn.)

I suspect not, a classic box just has three associated lengths so that 
pretty much determines
the "packaged" resize combinations.

But for a coffin the equivalent of height/depth is really the y 
coordinates of any handle
relative to the total height; and width similarly can be split by the x 
coordinate of any handle
thus I think there are too many possibilities to wrap these in simple 
named commands and the caller
will need to calculate the scale factors required.