I would suggest 2 improvements for Midi File import and export:
1.) When I import a midi-file into Reason it is imported to a new track meaning that you have to move the file/clip to the right place afterwards. If I import a midi-file into Reaper the file is imported to the selected track at the cursor position. This is how it should be.
2.) Since we have clips in Reason it should be possible to save single (midi) clips (e.g. a drum pattern).