I think the issue about comp rears its head because of one category - Overall Champion - and the fact that it has the most loot attached to it. All the other categories feed into "overall" - and thus if you have a Comp category - it pisses people off towards overall. I suggest that for a GT type tournament that you eliminate Overall from the categories. Have a Best General, Best Painted, Best Themed, Funnest Opponent etc category. You could even break it down by Codex if you wanted - or a 1, 2, 3rd place for each. Split the prize support evenly across those. Yeah - there may be less prize support for winning a category because you spread stuff out more. But at the end of the day, do people really play in tourneys for the loot - or for the fun of competing and maybe getting their 10 seconds of fame for winning something? I think most people do the latter. The more people who get their name called and get to come up front - even if it's just for a trinket - the better.
This way everyone has their "thing" they can go for. I'm a helluva guy and love just to play and have fun - so I go for funnest player. Kenny is a top shelf player - he guns for best General. Brandon..well shit - he wins all the painting stuff. Etc, etc...overall - I think more people have fun - get less bent out of shape about "cheating" and "broken lists" - are less tempted to cheat for the big prize - and you get more positive feedback on your tournaments.
I think we've gotten a little spoiled toward the 'ard boyz type winner take all tournaments - and forgotten about the overall fun part of what the GT's are - getting a bunch of guys who all geek out on the hobby together and getting to play armies/tactics etc you would never see in you local gaming scene.