What I had envisioned for the #builds channel was a repository that gave information about a build you wanted to share. The format to post would be a screenshot of your equipped gear in the menu along with an explanation that included any pertinent details (idiosyncrasies/unique techs, biomes where it worked really well, or whatever it was that made this build shine). I was thinking it would have a multiple hours long slow mode (3 or 6 maybe) attached to discourage too many discussion posts. Discussion would either be redirected into its own separate channel (#builds_discussion), or more realistically, just limited by the slow mode. The slow mode would enable you to talk about a posted build succinctly, and make it easier to scroll through people's builds without having to sort through 100 messages between them. This single channel idea would only work with slow mode- it would become just another chat channel otherwise.
I also don't think the screenshot should be mandatory, just what I think people will end up doing the most. It isn't necessary if you include your full build (along with any relevant affixes) in the text.
The build post itself could be posted by a bot if you wanted to enforce a format- but I don't know how much time/effort that would take. It's just a possible option rather than being part of the core suggestion.