First and foremost, races can be lost intentionally by failure to make a checkpoint on time. Is this acceptable? You could feasibly lose 10-20% of races and still win the circuit. Whenever the difficulty creeps up, you can just lose immediately, make the next race easier, and save a lot of time.
Secondly, two circuits will not have the same length, because they won't have the same tracks. There are 7 tracks to choose from (forward, backwards, or mirrored) and 26 races in the list. Even a single circuit getting Alcatraz (under 4 minutes done well) rather than LA or Hawaii (Likely 7 minutes plus) can make a huge swing.
Live timing also makes it advantageous to slam on the breaks right before crossing the finish line to advance the end of race screen faster. This is counter intuitive as well.
I think the best thing would be to have a category where you race the 7 primary tracks forwards and then backwards for a total of 14 races, or to have forwards and backwards as separate categories. Then use the best sum of in game times as the record. This would better incentive car selection strategy without it taking valuable extra seconds to do so. A 7 or 14 race category would be much more time manageable to run and watch as well.
I hope I've expressed myself well, as the circuit certainly seems like a lackluster category due to the reasons listed above.
On a side note, I'd prefer banning unlockable cars as well, but that's another story.
We should at least do like the original Rush game and require every course in the circuit have three completed laps. It would be more consistent across the series that way. 2049 doesn't have the checkpoint system, though.
Whoops, it looks like there are 28 races (7 Tracks, Forwards, Backwards, Mirrored, and backwards and mirrored). So every Circuit is the same length.
So I only have two suggestions then, both of which are rules in the original Rush game: requiring 3 laps to be completed for every track, and allowing the cheat that turns the game timer off.
If the original Rush allows the No Time cheat for the circuit, why wouldn't Rush 2? The circuit mechanics are basically identical.