Thank you for this. One potentially crucial thing worth factoring into the appearance-diversity consideration is that because of that Schelling effect, we could be losing really impactful people if they don't happen to feel at home in the white male-dominated upper-middle class category. (So maybe encouraging ambassador EAs who are part of currently EA-marginalized communities to host EA events and do EA outreach in those communities would be very valuable.)
Experience and opinion really have to be worked on more. Speaking from my own introduction to EA, at first touch the feel of "the EA community" was very exclusive and hostile, because even though I was already essentially a consequentialist and already wanted to have a high positive impact in the world, I hadn't thought through what most of the "EAs" I was meeting had spent months or years thinking about already, and even if something made sense as soon as I heard it and considered it, I felt negatively judged for not having already thought of it just because I hadn't happened to have previously had any prompting to consider that specific thing from any of the conditions of my life up until then.
(And yes, this was absolutely augmented by the male dominance -- which may actually be the entire cause of the sensation of being "judged" -- and it required the birth of close friendships for me to stomach sticking around and to learn to spend more time deconstructing my biases and assessing how to maximize my positive impact.)
Maybe EA needs some sociability coaches who can teach us (especially any of us positioned to help with the Schelling issue) how to build a sense of community with potential recruits, and how to start talking with those people about doing altruism effectively from where they are.