Mechanical assistance should be independent of class rating. There are many peaks I've done that I consider class 2 that a motorcycle could easily take you to the very summit of. We need to look at class ratings in the absence of vehicular support. You can stand on the top of a 5.12d without climbing an inch of it with the support of a helicopter. In fact,
The Palisade (YDS 5.4) has summit visitors from helicopter tours.
As far as class 1, the general consensus in CO is a trail or road takes you to the summit.
1+ is used here to indicate some off-trail (or overgrown trail) that is of little consequence vs. the trail itself continuing.
2+ used here means hands are involved, but briefly, and exposure with hands in combination is minimal.
3+ used here means not just scrambling, but high-consequence scrambling, where the moves are not as difficult as class 4, but an error is likely to be fatal.
4+ used here means harder 4th class, or a long pitch of harder 4th class. Some people have may disagreed about whether it is 5th class or 4th or it comes from a guidebook.
My observations, comparing to CA (and WA) standards (many CA class 1 from Secor are adjusted to class 2 on LoJ):
CA class 1 is anything that is CO class 2 and below.
CA class 2 is CO 2+.
CA class 2+ (often labeled 2-3) is CO 3.
CA class 3 is CO class 4.
CA class 4 is CO low 5th.
CA class 5 seems to begin at 5.6, with a few exceptions.
I'd say we could add a suffix to the class 1 rating to indicate a driveup, like "1-", but sometimes this can be a problem, like presence of gates and property circumstances. Seems like every year I go to repeat something that was at one point a driveup that is no longer so, with closures put in place by the authorities/owners that be. The one factor that is independent of this is how difficult it is via foot travel.
Probably best to add something in the notes of the class rating as a case-by-case approach is needed.