I wish there was a way for us to vote on the bug report/enhancement requests.
This one bothers the heck out of me too.
And while we're on the subject of Drum Maps... the Ctrl+Shft port change trick
described here gets my vote for the most arcane, yet essential tip ever...
If I have a MIDI track routed to my instance of Addictive Drums, and I select "new Drum Map" and select the XLN Addictive Drums preset, you'd think it would be smart enough to retain the existing routing to the plugin, but no... I think it goes back to the default MIDI port or something. Anyway... rant over.