As the topic states, what M&M books would be great selections for being revised to Third Edition? What books do you love and/or miss? How would you update them, or expand on the information in the book?
Personally, I liked the Mecha & Manga book. Simple, thin, cheap, and offered little in the way of new powers that couldn't be figured out by looking through the main rulebook/handbook. But it was great for pointing you in the right direction and showing you how to make specific types of powers in line with anime instead of having to do the work yourself from the ground up.
I'd love to see an updated edition version of this book, perhaps expanded upon with an actual Japan generic setting, and maybe some mentions of alternative settings in the flavor of anime and manga (like, of, I dunno, mecha in space?), and add generic NPCs, villains, minions, mecha, bases, etc, as well as the archetypes that were in the original book (expand on those too, btw).
I also loved Ultimate Powers and Time of Crisis. BUT, Ultimate Powers was surpassed by Power Profiles, which is still a great book, and Time of Crisis turned out to be less a sourcebook for Crisis stories (like DC's Crisis on Infinite Earths, Zero Hour Crisis in Time, Infinite Crisis, Final Crisis, etc), and more a premade adventure/campaign book.
Time of Crisis, or rather, the idea of a Crisis Handbook, I think would be a great idea. A sourcebook for an adventure, or even a campaign, where heroes aren't just fighting to save the world, but the entire universe, if not the multiverse or their entire timeline....or both! A sourcebook for adventures of the most epic scale, where PL X World devourers as presented in the Cosmic Handbook would be less the main threat, more an observer on the sidelines, and perhaps an ally against the godlike universe-destroying villain(s) when the story reaches its climax.
For inspiration on such stories, sure, DC has their list of Crisis events, but Marvel has had many of their own Crises in the past as well. Most recently in the form of Secret Wars and the build-up stories in Avengers comics (Time Runs Out, and Avengers and New Avengers series as a whole, w/ Avengers World playing a large part too). Onslaught and Heroes Reborn, as well as Age Of Apocalypse with the prequel Legion Quest would make good examples too, as a Crisis in Time where the world (or a portion of it?) ends, with heroes being reborn/recreated in an alternate timeline, and realizing that they must reset the timeline to its original form, losing what they perceive as their lives because the universe is going to end if they don't....you know, stuff like that.