I really don't get the need for the cover up rule and it doesn't bother me at all if cheerleaders walk around in their uniforms at comps - I've seen so much worse at dance competitions, and even then it doesn't bother me. Cheer comps require people to pay for admission, so that alone will keep a lot of the pervert element out more than other types of competitions (at a dance comp, anyone can walk in for free).
I've never really seen an all star cheer uniform that looks "inappropriate" (some NFL/NBA uniforms cross a line, yes, but not all star and HS, unless I'm in the dark or missed something). I also don't really get why a stomach showing is the standard that we regulate on - to me it should be more about skirt or short length and/or low cut tops (like the rules should be that their butt cheeks shouldn't be hanging out and there shouldn't be cleavage). I guess if the waist was mega low cut to the point where their hip bones would be exposed, then that would be a stomach issue, but I haven't really seen AS uniforms like that - most just go a little below the belly button.
I personally think cropped cheer tops are cute and can totally look very conservative if the rest of the inform is styled tastefully, and I'm actually bummed about this full top rule cause my CP would look much cuter in a crop top ;).