I like Brad's idea but I also like the original idea Chris came up with.
Giving the documentary a focus like what Brad talked about is very appealing. I'm familiar with the movie he referenced while talking about it and I will say it was a good watch. Of course, if the subjects you choose to follow aren't interesting enough to carry almost 1/3 of a movie then you'll run into problems. And with so many unique editors out there it would be a bit difficult to select only a few subjects. On the topic of the movie itself, while I enjoyed it overall I actually found myself biasing against some of the games that were featured because I either just didn't like their creators or lost respect for them as the movie went on. Was it an interesting look into the industry and some of the people behind it? Very much so. However, watching some of these people that were chosen as subjects actually made me want to distance myself a bit from it. The way they behaved and some of their thought processes made me actually feel a bit ashamed to call myself a "gamer." This is a possible risk associated with giving a documentary like this such an intense focus.
However, based on the way Chris describes his current vision of the documentary it actually feels lacking major focus. Obviously without a proper script in order that is going to happen but I think you need a balance of "character" focus and open questioning.
While you're questioning the editors I imagine you'll be seeing certain subjects pop up while they discuss either how they got into it, what they enjoy about it, etc. Subjects such as contests (online/convention), Iron Editor, Non-US influence in AMVs, etc. I would prepare a list of these types of things that I would consider major in the hobby, decide on the best people to follow around for them, and then do just that. Concentrate small but longer sections on these certain aspects of the hobby and by following people around, give the audience something more to hook into and identify with than an incredibly large collection of editors just answering questions.
Because while getting as many editors and opinions in there as possible is a really cool goal, you need at least a couple people that the audience can "like", if you get what I mean. Hearing a ton of people talk about Iron Editor is fun and all, but following two editors before they face off, capturing the before, after, and all that they go through and feel would be a great experience for those that don't know what it's about.
I'm with Douggie and agree that you should do a Kickstarter or something along the lines to cover travel. Figure out the basic script and flow of the video, pick certain subjects to follow, and travel to cons.
If it was me, I would personally go in this order....
The rise of Kazaa/Limewire - Basic discussion about how AMVs first started spreading online.
AMV Contests (Convention) - Quite a few people had their first experience with AMVs from randomly wandering into the AMV contest at their local convention and decided they wanted to do it for themselves.
The Creation of the Org - People are discovering videos online and off, now a place for them all to congregate has been created.
AMV Panels/Iron Editor - The hobby has been given legs, people are finding others that are like them and now they're trying to drum up activity and gain additional attention.
European Influence - I would actually want to travel to Europe for this one. I would either hit up Japan Expo as the largest con or Connichi as the one with the largest amount of editors in attendance (possibly both). See if you can arrange some interviews with international editors to talk about some of the heavy hitters that really influenced the hobby. (AbsoluteDestiny, Tyler, Nostromo, etc.) I imagine that a large amount of the doc will be about US/Canadian editors so being able to capture at least part of what the European community has helped set in motion would not only be a great way to talk about how trends/styles changed and evolved based on popular editors, but it would help give the viewers a better idea of just how far this hobby has spread.
Online Contests/Growing Online Communities - With the hobby growing, spreading to different countries through Youtube, AMVNews, The Org, and more, online contests such as Big Contest, Akross, and even the little ones we run on the Org have become great ways for editors to meet, make some badass videos, and build friendships. The current online contests/other online communities are huge parts of what make the hobby what it is today. It would be a missed opportunity to not acknowledge the amazing videos and editors that have become well known thanks to these resources.
Finally, the editors - All of the previous topics really come down to this since at it's heart, AMVs are really about the community. This would allow you to go back to all the previous sections of the doc and give them a proper ending by showing what this is all about. The online friends meeting up, the finalists of contests congratulating each other on wins, the Iron Editors having drinks together after a stressful event, the glorious dancing of JCD, and all the rest. Tie up all the stories with a neat little bow and give it a happy ending.
And of course, let me know if you need anything

I KNOW EVERYONE.