So after playing almost every other day I am wondering what the possibilities are for creating a full on campaign with the stories given. There's obviously a few things to consider such as death of an investigator, rewards/punishments for failing and/or winning objectives, and story continuity, etc.

I'd love to hear some thoughts for the "campaignability".

With 8 characters I'd turn it into something of a stamina run to see which group lasts the longest. Granted, you can only really do either teams of 2 or either teams of 3 plus a benchwarmer or teams of 4. The problem with 2 could be that a single player has to play by themself if their partner died, but it could be a character run instead so they can join another solo player. For 4, you could tally the wins/losses, surviving characters, streaks, etc. between the two competing teams. It'd probably be more fun with 9 people who play so there's some actual competition, but that depend on the group you have.

As for match synergy, I'd say you can only change your skillset if a character is removed from the game (the rest of the team would have to adjust to make up for the loss) and they can only carry over items equal to their starting number. None of which can be mission exclusive of course.