Currently setting up and changing your rules on the Marketing Channel Report is quite tedious and error prone.
Any changes take 30 days to remove any tags that have been set on the visitor.
It would be nice to make a rule change and preview (based on the last 30 days) what the report would look like given the new rules.
It would be even nicer to then clear that history (see this post) so I don't have to wait 30 days.
It would be nirvana to then update history and apply those rules to the last 30 days.