Did anything become of the Memod manual idea before Memod was cancelled?

I assume you are referring to the idea of a making-of documentation type thing. Nothing happened with it - the devs said that much of it was "innapropriate" for the general audience. The concepts and ideas could be released, assuming that they're released as just that - simply a collection of concept art and ideas with no relation to MEMod; however, I doubt this will happen. I would like to see it just as much as you, but I wouldn't count on it.

If that's not what you're talking about, then I can't help you.

The manual would have been among the last things to be completed, since it would necessarily evolve alongside the implementation of our design ideas, and be subject to constant revision to ensure the information contained in it is accurate.

I'm not aware of any other dev working on a manual as such - though some of our design notes would probably have been suitable material for inclusion - and at the stage MEMod was at in the months preceding its termination, it was not a priority for me.