Some time ago, Kevin Crawford published a new class for Scarlet Heroes and B/X compatible retro-clones in his Sandbox magazine, the Blademaster. It was rather uncharacteristic for him and for the ruleset, in that it took clear inspirations from the maneuver system of Tome of Battle, a 3rd Edition sourcebook controversial for its time in using a pseudo-Vancian system for martial moves and techniques (several of which were clearly supernatural in origin). Even many D20 fans didn't like it, believing it to be broken and overpowered. The truth is that this is a common misconception, at least not in comparison to the options already present in the corebooks, but that's another discussion for another time.
In regards to the OSR, ToB's maneuver system isn't exactly what I would imagine being in line with many of its aesthetics, considering that its fanbase tends to want different things out of a D&D game than what old-school retroclones do. For one, ToB's fanbase tends to prize class balance as a virtue and have a preference for higher-powered playstyles in comparison to the down-in-the-muck lethality of many retroclone adventures.
Still, Crawford managed to do a good job with the Blademaster, and if I had to pick an author to present a potentially unpopular idea to the usual demographic, he'd be my first choice. Honestly, I feel that if an OSR author with little name recognition or did not have a stellar track record tried the same thing, he probably wouldn't have gotten many grabbers.
Who Would You Pick to...?
So, if you had to implement a choice in the table-top fandom which has a chance to be unpopular, which game designer/personality would you view as the best option for wooing over the other side? Let's assume you're publishing a third-party sourcebook for the opposing demographic, and can choose said designer as the main writer.
Just to start off with some examples, who would you pick to...
1.) implement an alternate spellcasting system to Vancian magic for Gygaxian purists?
2.) create a "dark superheroes" Vampire game for World of Darkness "crapsack world" fans?
3.) write an old-school style "DM empowerment" rules variant for 3.X/Pathfinder fans?
4.) to write a setting with anime art and aesthetics for OSR gamers?
As for my choices...well, I'd like to hear yours first, and I don't know whether or not my own would influence your decision, so highlight the below to get the answers.
1.) Frank Mentzer. His close work association with Gary Gygax and ability to revise rules on the Dungeons & Dragons line resulted in many popular and iconic pieces, and worked on The Book of Marvelous Magic.
2.) Steve Kenson. In addition to working on material for Mutants & Masterminds, he also did some writing for Aberrant back in the day.
3.) Bill Webb of Frog God Games. He and his team have enough experience in OSR and Pathfinder rulesets to translate well between the nuances.
4.) Again, Kevin Crawford, hope that's not "cheating." Exemplars and Eidolons does a good job of replicating some of the higher-powered moves as seen in some of the shows, and his Red Tide setting does a good job of combining both Western and Eastern setting tropes together.