Maybe a new feature could be implemented:
Rearrange Ableton set.
This would do time cuts and time pastes in set so the ableton set gets rearranged following ableset.
It would be a one time button with the “undo” option (same as “place locators on clips”).
With the optional parameter “leave x bars between songs”.
You hit that button and wait.
Then you would simply export your set from ableton as mp3.
EDIT:
added feature request for this feature