What if you could take an RPG and rebuild it with only the parts you like, toss out or change the parts you didn't, and come up with your own game from it? That's what they did with Dungeons & Delvers. You can check out the Red Book Kickstarter now.
From the campaign:
In a nutshell: the World’s First Roleplaying Game how I’d do it. A hack that does what I always wished the game would do, that changes or discards the bits and pieces that always rubbed me the wrong way, while not overly complicating things and still delivering the same classic dungeon-crawler experience I’ve loved since I was a kid.
Don’t get me wrong: I’ve enjoyed the game for over twenty years. I wouldn’t have kept playing it and writing about it if I didn’t. But everyone has their issues with it, everyone cooks up their own homebrew rules whether or not they end up using them at the table, or even bothering to fully flesh them out. I just ended up with enough that I felt collectively it justified a new game.
People have described it as a more customizable-yet-simpler take on 5th Edition, something between 3rd and 5th Edition, and even a kind of modernized B/X or Rules Cyclopedia. Pretty much everyone agrees it fits the old-school aesthetic, which is good because it was intended to be a kind of homage to the "easy to master black box" that I grew up on.
The campaign's around 3/5 funded with 17 days left to go.