Having some Horizon style open world areas around each track could be fun since you probably need to build and detail quite a lot of that anyway. Let us drive around it a bit and create or race extra areas nearby, from the nearest airport (that we can also race on) or something. Let us add some karting tracks to any tracks that might not have any.
It would be cool to be able to drive through the pit areas and to the parking lots and the entrance. You always see RVs and trucks around the track but no way to access those areas.
They could showcase the whole circuit this way and for online play you have cool meeting areas like in real life!