Considering that a good amount of people just straight up skip and never touch F2, I don't think F3 is required. Sure, could be nice to have it, but I don't think many would be interested.
Porsche Supercup on the other hand, potentially could be implemented as it would be a sidegrade to F1/F2 (something different than open-wheels of F1/F2) but Supercars in F1 23 are already difficult to handle, so it's difficult to say whether it is necessary.
Tl;dr:
- F3 is a no from me, as F2 already is barely touched by many
- Supercup is a maybe
Yeah I play F1 games solely for F1. Rather more features and depth added to F1 not new race series
