As someone who is emerging into the pinball see and has watched most recorded PAPA footage, I can tell we've come a long way. Starting in the days of post-tournament recording where the big plays were known and the winner was determined, only a limited amount of technology and casting experience was available. One camera over a game was the norm, and a handful of events and games got recorded.
Compare that to today, where we have Telestration, multiple setups with multiple cameras for players/tilt bobs/DMDs, software that allows for a variety of during-production changes, Twitch.tv, and casters with years of experience on the IFPA and PAPA crews. We should be using these tools and toys to their maximum potential, for the benefit of casual and competitive players alike.
But first, I have some ideas for one of the big suggestions mentioned a few times in this thread: storylines.
If you look at modern successful Esports, which is primarily broadcast on Twitch, you can see various games with players who become household names even to the casual viewer. I don't play competitive Super Smash Bros, but I watch every major to cheer on folks like Hungrybox and see a new chapter unravel in the scene's lore.
The Smash Brothers documentary did a lot of this work, and pulled people out to watch. Now while this is an extensive project and not feasible for a short-term goal, once some baseline interest and lore comes out the pinball community can look towards a project of this magnitude. How can we get there? First, using the aforementioned technology, put together player profiles for the key players in a tournament. Show a picture, name, key tournaments, IFPA rank, seeding, and so on and swap it over a camera (player cam, most likely) for a few seconds while the casters discuss the player. Some people might find a player is local to them and get drawn in, others might hear of a cool story and will go check it out.
Another way to bring more people to the lore is to make it digestible. Twitch has an amazing highlight system that can ration off series, flashy saves, or crazy balls into bite-sized content that's easy to market instead of 8+ hour videos where the highlights aren't prevalent. If there's time between matches, show some highlights of the upcoming players using this footage as well!
Now that a lore is set up and people might be drawn in, it's time to hook them by helping them understand what is going on. I've had a few ideas tossing in my head, with two major concepts sticking out. First is to incorporate explanations and core concepts into the broadcasts. Have a "teaching" caster who specializes in knowing rulesets and pinball mechanics who can explain them in an efficient and easy to understand manner. Prepare cheat sheets or rulesheets on every game in the tournament bank for the casters to utilize. For all casters, be observent of the state of the game. Many a time I sighed to myself saying "that's not right" when a mode is falsely believed to have started or a strategy-altering change to the game state is missed. Note taking is good!
The second option is to have a "beginner-friendly" stream or set of videos that caters to the beginner player and talks about pinball mechanics, strategy, and rules. Splitting the stream base might not work for smaller broadcasts, but youtube videos in post-tournament could work! I plan to do something like this in the future to help someone in my shoes a few months ago.
On that second stream conversation, there are a lot of games wired up in a tournament bank. Unfortunately, only one game can be cast at a time. If broadcasts get more viewership, a second stream could be added to show other games with/without commentary to provide choices for viewers. And for those who don't wish to choose, Multitwitch allows them to watch both simultaneously!
I can ramble on about this, but it comes back to two things: enticing viewers to watch and drawing them in with stories and easily accessible content, and using the power of technology and design to drive up production quality and make the experience more enjoyable for everyone. I'm willing to help with or discuss any of this, especially the PAPA folks since I'm a Pittsburgh native. I want to see pinball grow, and I feel this is my way to do it.