Not an original idea by any means but maybe if we could find a way to encourage the usage of backpacks we could see less stalemates. They'd give teams another reason to push and different teams/maps would use different banners which would make things more interesting from a spectators standpoint. I suspect that a lot of spectators who dont know anything about comp have a hard time seeing the differences in playstyles. 6v6 is symmetrical in team and often weapon composition most of the time so making teams more easily discernable would give new players something intuitive for them to analyze. They also make the stalemates themselves a little more interesting since spam actually leads to something.
That being said, there are definitely some problems with banners. They gimp you so fucking hard as a soldier until you can actually use them so running them on mids is almost never a good idea. Though I guess that is a good thing becuase it encourages aggressive mids opposed to 2009 style waddle pocket mids. In comparison to mediguns banners are very hard to track becuase they charge through damage and not through something that can be done at a consistent rate all of the time. I don't think there needs to be a huge change in how they charge, but making it more visually clear to players that someone is wearing a backpack and making it more obvious when someone's banner is charged would help a lot.
Now that i think of it, It would be pretty cool if valve gave demo a backpack. Im a terrible demo so im not too confident in the following but I believe it wouldn't have the problem soldier does with banners being a huge gimp until they're actually charged.