Joseph Wright writes:

 > I can see your argument for creating instances with only minor
 > adjustments from existing ones ("All I want to do is change length a to
 > length b, leaving everything else alone."). My feeling is that the idea
 > is that document classes should be much clearer on the settings they
 > use, so the cost of copying a template and altering only a few lines is
 > worth it in clarity of what is going on. The danger of allowing
 > something like \EditInstance is that you can easily get back to ad hoc
 > changes here and there with no clear separation of design and document
 > code.

that is a danger and it is something that needs to put into the equation when
we decide whether or not to offer such an interface for small design
adjustments.

My personal feeling (at the meoment) is that LaTeX in the past did fairly well
by offering a balance with separating design and content, ie always allowing
overwrite possibilities if needed even in mid-document if desperately
wanted. As a result such documents meant hand-tuning and they didn't work if
one changed the design overall, but on the other hand this is one reason why
you get higher quality in the final product compared to documents that have
been 100% processed by simply applying a style from the outside.

In other words I don't think that it would be really bad to offer it,
eventually.

frank