possible new sort option

Hello all,

Too much idle time, perhaps, but I've been musing on mailbox sorting.   
I mostly use JWZ sorting, with increasing dates.  This groups messages  
per the JWZ algorithm, and then sorts the groups by the increasing date  
of the first message in the group.  If I click on the date colulmn  
header, it simply reverses the order of presentation of the groups.    
In other words, the ordering within groups is not changed, but now the  
groups are sorted by the decreasing date of the first message in the  
group.

I have several mailboxes (mainly various mailing lists) where I'd like  
to maintain the message order within the groups as above, but sort the  
groups by the date of the most recent message in the group - either  
increasing or decreasing.  This would bring the most recently active  
threads to the top or bottom of the list.

Can anybody give an estimate of how difficult this would be to  
implement?


Jack