If you have sixteen entrants (as seems likely), have the final on the Saturday night rather than the Sunday morning. The final can be a longer game so a better test of skill and if it overruns it can be finished Sunday morning. Then you don't have the situation a few years ago when the final didn't get finished and the players met up later to determine a winner.
I like the mystery scenario in Double One, but this should only be for one round. It's handy publishing the rest of the rounds in advance not so the top players can shark (everyone who is arsed can prep) but so you can play without people spending ages on set up (and other people sitting round doing nothing). Plus people bringing a small travel kit need to know what to bring. In fact a max time limit to set up may be in order (30mins?45mins?)
For the scenarios, variety is key. A bit of this and a bit of that. One PTO round with 2 PTO and one other scenario - so the people determined not to play PTO can escape if they meet a like minded soul.
I prefer a completely random draw for all rounds. Seeded vs lower-seeded may be objectively justified but I think it discourages the lower seeds who can dream of a favourable run to the final...instead of expecting to get knocked out in round one.
You don't have to be too radically different - the key is picking good scenarios.