Go with Flash for now. He's pretty straightforward and won't require you to know a whole lot going in. His pressure should really do well in a tourney where guys don't know their character's priorities and the matchups versus his stuff yet. Plus time slow will really throw them off.
Batman has mixups, but we are seeing some stuff as unsafe on block so he'd be someone with potential, but you'd likely be blowing meter constantly just to have insurance on your stuff since no one knows if they have durability, armor, or priority enough to handle each other at times. He'll probably be good, but I bet it wont be till after lab time after launch. Play it safe.
Sinestro would likely be a solid choice after Flash. Lots of tools at any range and easy looking mixups and resets of summonable low launchers and grabs.
Green Arrow has potential, but his slide is unsafe and he has some slow normals so your reaction to pressure with him without lab training will be key. Plus don't fish too many times for gimmick arrows. He's vulnerable during that and you should do it after a knockdown or they whif majorly. I'd use him, but I dress as the guy too. Possible solid, but stay out on folks.
Catwoman looks good for pressure, but dont get zoned.
I say Sinestro or Flash since they look easy to get started on their offense and easy to stay safe. They just appear straight forward to me with lots of potential.
