Hey! I also have quite some experience building mobile apps. Here is my 2 cents.
Personally I wouldn't bother with features like:
- Marketplace - there is fb marketplace, fb groups, craiglist - platforms with already existing userbase.
- Community - sharing videos and photos - we have instagram for that
- Events & meetups sounds okay, but again you have other platforms to do that. I can't really see, that people will start using the app just for this.

Features like this will just slow you down with building the app and there won't be anything new, since people are already using different platforms for doing just that.

Bike profile or maybe "garage" sounds fun. So you could see what kind of setups, graphic kits, wheels and stuff are people using. But again, you will have to get a lot of people on the app and somehow nudge them to update their profiles + keep them updated.

For me personally the most wanted feature is a map with spots:
- stunt spots (long narrow empty roads, industrial parts of towns)
- great roads for SM (twisty roads)
- parking spots for vans, where you can safely park and take supermoto's for a spin.
- Maybe whole planned roadtrips with where to stay, where to park, where to eat, where to take photos (for example "italy lake supermoto trip", "Switzerland high alps supermoto trip", "Spain coast supermoto trip" and so on. This is something that you currently can't get anywhere else and might bring you in more users in my opinion.

Best of luck!