Thanks everyone who gave me feedback on DF futures.  

The most popular enhancement seems to be keystroke reconfigurability -- 
most thought function keys and other strategic keys would be sufficient 
(I'll be interested in hearing what everyone thinks the strategic keys 
are).  Also popular was an additional function key menu which would 
certainly be added together with function key reconfiguration (since 
either change requires manual reentry of user configurations).

Second in popularity seems to be a directory tree popup.  To be honest, 
however, this is much less certain to implemented since the effort (and 
code size, memory requirements, etc.) to add this are much more 
substantial.

Marked file functions and better editing at prompts seemed to be about 
intermediate in popularity.  I interpreted the reaction as "nice to have 
but not something to get enormously excited about."  Since these 
enhancements, while non-trivial, are not huge efforts either, they are 
certainly possibilities.

Neither 4DOS/NDOS support nor color-coded directory entries appeared to be 
big hits.  I'm still kind of attached to the idea of using color to signal 
file differences between source and target directories, so who knows?  I 
included 4DOS/NDOS because this is something a few people have requested, 
but this seems to be a minority opinion.

Thanks again for all your help.