Well, I think it would be up to the Admin to set the classes.  Perhaps going by the number of models an entrant has under their belt.  Let's say 3 classes. Beginner-under 50 models, intermediate-50 to 200 models and expert 200+ models.  These numbers are just examples.  The entrant would determine their class by submitting the number of models they have built in their lifetime.  Yes, the honour system enters into the process.

  Would attempting to level the playing field be seen as a negative?

Not really any issues here Iain.  Just a friendly debate/discussion!  I do see a major flaw in your sports analogy.  I mean, the beer league players don't run with the NHL'ers.  The NCAA'ers don't run with the NFL'ers.  See where I'm going?  There are many, many different classes for people to compete against others of equal (or close to equal) skill and ability levels.  Those in the "lower" classes still look up to and admire their idols in the "upper" classes!  How many kids or teens said to themselves "I'm gonna be like Wayne Gretzky" while playing city league hockey?  How many high school kids said "I'm gonna be like Micheal Jordan" while playing high scool ball?  The incentive is still there to improve and emulate the greats.  Like I said in an earlier post on the topic..."I'm ecstatic that we have a handful of members here at SMA that are quite literally, world class modellers!  It's been nothing but beneficial to the site and personally, I've learned a ton from these Guys!  Extremely valuable to have the examples and resources some guys contribute...No doubt about it!"

  I guess what I'm trying to say is that a level (or more level) playing field doesn't have to segragate or alienate anyone.  Everyone concerned would still have full access to each others build to follow and admire.  The only separation would come at evaluation time.