All these new feature suggestions/possibilities sound great, and Maemo Mapper is already one of the best free applications available for the 770/N800.

Personally, what I'd like to see that I don't think anyone else has mentioned:
- Increased stability
- No-map mode (just display blank tiles, maybe a grid?)
- Ability to browse/search through the POI database
- High contrast mode (not sure how this would be done..)
- Thumb mode (put some big useful buttons on the left/right of the screen)
- An option to automatically retrieve the reverse route when downloading a route (and append/queue it to the first route)
- Further Open Street-Maps integration (ability to upload tracks/open browser with editor, etc.)

With all that said, Maemo Mapper is already great - anything extra now is just a bonus