Are you seriously saying that you see no advantage in designing your deck after everyone else has posted theirs?
Yes. I'm seriously saying that the advantage is non-existant. It exists in some player's heads, but it's not actually going to affect the results of the tournament at all. If people want to delay signup because they seriously believe an evil genius cares about their specific deck enough to counter it, that's their choice, but it's not actually going to happen. As previously stated, even if someone bothers to try, they're basically asking for average results, because the chances they'll get 1 or more opponents that are in the 50% they didn't design to beat are pretty darn high, actually.
This does, of course, assume that players are smart enough to look at the other decks their team is registering and play something different enough to not fall to the same counter-deck. Maybe that's a bad assumption on my part.