My favorite events are the rally car races and tournaments. How about ramping those up a notch with some events that simulate, as best as can be done, BAJA 1000-like, off-road races? There are lots of great models from many different diecast manufacturers which would open the possibilities of lots of different types of races.
You could do tournaments based on manufacturers (e.g., Land Rover, Jeep, Ford, etc.), by type (e.g., lifted/stock height, trucks/SUVs, stockers/racers, etc.), by age (e.g., classic 4x4s, modern SUVs, etc.) and probably many other categories that could be identified. And while I’d personally be more inclined towards the realistic models, Matchbox and Hot Wheels even have a lot of cool “fantasy” 4x4s that would be interesting (e.g., Matchbox has the Dune Dog, Land Rover SVX, Rock Shocker, MBX 4x4, Jeep Hurricane, Mudstanger, Ridge Raider, Sonora Shredder, etc. while Hot Wheels has the Land Crusher, Monster Dairy Delivery, Big BelAir (coming), Dune Daddy, Sandivore, Mountain Mauler, Baja Bone Shaker, Bad Mudder, etc.).
Obviously, due to the limitations of diecast models, you couldn’t get too crazy with obstacles, jumps, rough terrain, etc., you guys are creative enough that I’m sure you could come up with some things that would give the events that SCORE feel and still be workable for the vehicles. Given the proliferation of off-road models the last few years—both realistic and fantasy—you can see their popularity and I’m sure that would translate into interested viewers for your videos.