ABCD.... Am1, Am2,... Adv, Int,... Doesn't really matter to me.
How about a different approach? Change the division ratings to accommodate better flow to the next level. This is based solely from a competitive perspective/motivation. Maybe from low to high:
Novice- <701
Rec- 701-870
Intermmediate- 871-935
Advanced- 936-999 (980 might be better, but work to 999)
Pro- 1000+
Novice becomes more of a true novice or really bad player, which is who novice players should be up against.
Rec- players are "forced" to move to a more competitive level, but with work almost all players can get to 871.
Int- the ratings bracket is much larger than before and "forces" players to get better to win, or be stuck in the purgatory of Int that I think it should be.
Adv- the ratings bracket is much larger than before, and provides those advanced players a large amount of time/skill before being required to move up.
Pro- there aren't many of these, but there shouldn't be. If you are currently 970 rated, you can play as a pro and would likely still play with 950-985 rated players at most A tiers down.
Remember, players can always play up. To me it's the bottom of the bracket that matters. I can hear a lot of moaning from those 874 players, but remember this is based on competition and not if you personally are winning. I think disc golfers are too selfish and greedy anyway. "Dude that player's pack doesn't even have a car in it! I'm not playing." How about, "Here's a disc with our tourney stamp on it. Want anything else? Finish in the top 20%!"