I know it is a major pain for PCI, but possibly each BI could have a format similar to this:
Scene 1 - Common scene where all the heroes face the same foe/scenario. For example, "you are all outside the city after learning of an invasion and now have to return with enemies at your heels."
Scene 2 - Variable encounter with three different missions which can be chosen by each table. Allow 5 minutes for players to change tables if they desire. For example, you could have the usual 'hold the gates' (melee-heavy), 'hold the walls' (ranged heavy), or 'special mission' (such as a roleplaying encounter to rally troops and negotiate tactics/command/etc).
Scene 3 - Common scene where all the Heroes from the previous Scene must face some kind of challenge. For example, "enemy troops have managed to find a tunnel into the city, and you have to defend X civilians who are trying to escape." (sucks for 'non-combat' types, but sometimes you have to get your hands dirty I guess
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Scene 4 - Variable encounter with three different missions which can be chosen by each table. Allow 5 minutes for players to change tables if they desire. For example, you could have a 'hold the city' encounter (combat heavy), 'infiltration' (stealth-focused), and a 'special mission' for some plot device allowed by only a single table based on success rate (as reported by GMs)?
MEAL BREAKContinue this alternating scheme after the break, until we reach the crescendo!
I know a lot of BI's already do this to one extent or another, but I personally always feel rushed whenever I play and this gives people the option of switching tables. Hell, as with the example of 'gate/wall/negotiating' it can add variety for the next scene where you face common enemies based on where they were at the time. For example, anyone defending the gate will be plastered against the wall and have to fight their way out, people on the walls will be able to snipe enemies but otherwise let baddies kill civilians unchecked, and people 'negotiating' will have to defend NPC's while the baddies swarm whatever building they are in (close quarters combat in a small room).
I know we can't do cookie-cutter things, but it is a thought.