There's a significant issue I need to tackle regarding the framing of the campaign: is it more Earth 1 or Earth 9?
To put that in English, one of the things people love about the Silver Age heroes (i.e. Earth 1) was the outpouring of creativity for the re-imagined characters. There really were no carry over villains for the 'new' heroes (Green Lantern, Hawkman, Flash, etc.) and limited ones for those that had been in continuous publication where the demarcation between 'worlds' was less clear. Everything was new and fresh and vibrant (and sometimes downright goofy) and those creations were the foundation of everything we have now. It would be great to have Earth 10 be full of as much of the same new ideas as I can muster.
One of the things people love about Earth 9 (and the DC Animated Universe, the Arrowverse, Smallville, and I suppose the DC Cinematic Universe if there is anyone who loves that) is that they re-imagine all of those ideas from Earth 1, as well as ideas from Earth 2, and mix and match them. It is an enormously fun sandbox to play in, and it's what people expect when you say you're playing in the DC Universe. The issues, to me at least, are that,
1) as proliferation of stuff in the Infinite New Final 52 Crises era is that wedding yourself to that can put walls around your sandbox.
2) as I said, it's been done well in a couple of different places. While I started this experiment as a "what would my DC Cinematic Universe look like" I want to make sure I'm not just retreading.
To do that I'm putting in some ground rules for myself (and to an extent my players): I'd like to present/develop a 6 character rogues gallery for each hero, and no more than 4 of those can come from existing continuity. For the team itself I'll follow a similar set of rules - one half of the villains I introduce have to be entirely new. The other half can come from either Earth 1 or Earth 2, but need to be re-imagined.