Hello there !
To be honest there was a contest I wanted to join but couldn't because of operation guys not wanted. I would love to maybe try another one.
For the LD/LA thing, I think Tf2maps did the same a long time ago, they have also some great concept for a contest like the connect 5 . To be honest I always thought that art and design should evolve like a tennis match. Some design choices tend to change when art is coming through and I don't think this kind of contest can propose that.
Or you make like the Artpass contest on TF2 where everyone is working on the same layout. The cons is that at the end there is only one map with different looks and you don't see a lot of them really played and it's kinda sad... (Also I migh won if you propose that contest ) You could still ask Valve to give one of their unfinished layout for the contest, hehe.
If you really want a cool contest, but it's just my opinion, propose something else than just doing the next competitive shit. I remember the day on 1.6 when we had tons of fun and interesting maps and when the hostage gamemode was cool (breaking into a house from every corner was nice) + we also have assassination and escape maps. Aww man...