For the list of columns they would like to see a normal select box with in the 
first item "Select a column" or something, but you mentioned there were some 
issues with this kind of solution?
 
The only issue was the formatting.  The column names in some cases get 
incredibly long making for a very difficult interface and poor layout. This in 
combination with the need to specify attribute type meant that a custom pick 
box needed to be developed.  I guess the issue here is that users don't 
readily understand that it is a button to be pressed in order to change the 
selected column, correct?  I can look at re-doing the interface as time 
permits.  Please file this as an enhancement.