I think that the "Default race settings" and "Modified race settings" are good for individual levels but they are not good for full-game runs. The problem is that, in MRS, there's written "You must start from a new player" but you can modify the settings of a race only when you finished it at least once. So I suggest to remove that rule in order to make the category possible. This will also make possible the use of the GTR-1 (or any other car) since the beginning of the game
I'd be in favor of scrapping "modified race settings" from anything other than individual levels, personally. We're already using the gtr-1 for like 90% of any% already. IMO "New game+" categories don't make much sense if leaderboard activity is low and potential time gains are minimal.
The main idea was pretty much to be able to have no traffic and good weather (also has significant effects on the crash courses), though you'd have to back out of each race in order to set race settings, which wouldn't even be worth it except perhaps for some circuit races? Having the Panoz GTR-1 from the getgo would be a nice touch, but perhaps it's indeed not worth having as a "full-game" category.
MRS is not so different from DRS in "All Races" and in "All Checkpoint" because you unlock the GTR-1 very soon. "All Crash Course" is a lot different because you're not forced to drive the Mustang Fastback and the London Cab. Also "All Blitz" and "All Circuit" are very different because, if you start from a new player, you can't drive the GTR-1. I think that the MRS is useful for some category, so I think we shouldn't eliminate it.
I added a separate "new player" variable similar to "race settings" except with language more suitable for the full-game runs.