pawsplay
Hero
Its possible to take an existing paradigm and build a unique setting with a minimum of new crunch. Eberron is proof of that.
A 3PP Eberron would be crippled. The "minimum of new crunch" you are talking about would include, at the time, a new base class, numerous new feats, the equivalent of new paragon paths, at least three new races, and several new types of magical items. Realistically, I don't think the 4e market for such a thing is much bigger than the Pathfinder market, and depending on competing 4e options, could be a good deal smaller.
If you want to be a 4e publisher, here's what you do:
- Get together with a half-dozen of your favorite 4e would-be 3PP friends
- Find, hire, or enslave two or three programmers to make an open source, non-infringing, offline character creator tool
- Spend your own resources to create the module needed for your setting to work in aforementioned tool