DW really needs to have a booklet or something on the meta game for creation.

I know you can reverse engineer etc etc. But really, it would do good to allow the GM into the meta game to allow him to make his own classes, or atleast give guidelines... or does something like this already exist and I am just blind?

The Advanced Delving chapter goes into some detail about creating content for the game, but if you want more information, it's going to take some question-and-answering.

Good thing we have forums!

Yeah, all that info is in Advanced Delving. It's got rough guidelines for classes, monsters, and moves. They even do a step-by-step breakdown of how a Move evolved over time, and why. It's a pretty helpful glimpse into the "behind the scenes." Really, though, DW has a pretty transparent engine and there's not a lot hidden away.

Evenglare, between this forum and Google+ you probably can throw ideas around and refine them with the feedback received, there are quite a few good things hidden inside this very forum, for example.

Also, my buddy Emong wrote up a good resource for Compendium Classes specifically; it's in the Beginner's Guide and he explains the concept pretty well, I think.

Really, though, I think that between Advance Delving and the many fan-made classes out there, it's easy to get a grip on what it takes to make a full class. I agree that I'd like to see another resource book. Mine was geared toward the basics but an in-depth collection would be awesome to see. Hopefully someone does this in the future.