Well conquest is not nearly like the push 5-cp gamemode of TF2. It would be more like a gravel pit where all caps are open at the start and either team can cap all three points. I fear that would be a bit too messy though. Nobody would know where to run, and the excellent gameflow in tf2 built around ubercharges would probably be broken.
(The reason why havent entered any of the contests thus far is because) I think there's a problem with the contests always trying to do something new. It's hard to come up with something in a gamemode that you don't know how it works (or if it even works) whatsoever. We saw a few neat takes on the push ctf gamemode but as many failed, nobody really likes PLR due to it's very imminent stalemateness (correct me if I'm wrong) and competitive ctf is broken since 2007. If we'd focused on gamemodes that we know and where we can take inspiration from existing maps, I think the chance of producing good maps is a lot bigger!
My proposal for a contest is simply A/D cp - a gamemode that most people love in both Dustbowl (despite its flaws) and Gravel Pit (which is one of my favourite TF2 maps both from a pub and comp perspective). This will give people rather free hands to do something new, while still sticking to a gamemode that we know works!