I've been working on D20 Modern for over 5 years now, and at this point, simply because I'm one of the few authors publishing under that ruleset, and not under the more profitable D20 Fantasy / D&D Engine, I consider myself an expert on D20 Modern. I've done some interesting stuff with it, produced some variant rules that both push the system forward and effectively emulate the media I've set out to well... emulate.
That said, there's alot of good rules I've created that I would like to see other D20 Publishers expand upon. It's all OGL to begin with, so take advantage of it, and use my ideas to push your own games forward.
I produced ALOT of good material for D20 Modern working with Louis Porter- I'd like to see the skydiving rules from Adrenaline Surge (2006, LPJ Designs) used in other contexts. Likewise, the archery rules and equipment from D7ACU: Perfect Archer (2007, Skortched Urf) adds alot of flavor to the games, and provides a nice alternative to guns.
On a larger note, I'd like to see the torture rules from Tell Me Now (2006, LPJ Designs) used as a basis for other opposed, complex skill checks. I could see the system powering that suppelment easily be adapted to things like computer hacking, forensic invesitgations, medical drama.... any time where one party attempts to solve a very complex problem or wear down the opposition through skill and tenacity. Hell, it's a damn fine rule for torture as is.
In terms of more complex ideas, I'd like to see other D20 Modern publishers expand on my ideas of Intermediary Classes (2005, LPJ Designs) and Affiliations (Otherverse America, 2009, Otherverse Games). Intermediary classes are story-based starting classes, not attribute based ones. You might play an ER Intern, or a Blogger instead of a Smart or Charismatic Hero. Intermediate classes are more powerful, but more specialized and less customizable than a Basic Class, but not quite as good as an Advanced Class.
Affiliations are basically like the X-Box 360's Achievements for Otherverse America.... you earn them by meeting specific feat and skill prerequistes and serving with a specific group, who trains you in secret techniques. Affiliations in Otherverse America can be famous military units, criminal gangs, political groups, terrorist cells, corporations, cults.... basically in exchange for cooperating with the GM in buildling a character that's an active part of the world, you are rewarded with the equivalent of a minor feat (and bragging rights) for free.
It's a concept that I think can be easily ported to other games, including fantasy ones. Anyway, that's just some stuff of mine that I'm especially proud of, and I think you, as readers, would enjoy.
Talk to you later,