You have lots of good points in your post anon. And certainly there are a number of ideals for owning robowaifus portrayed in books and movies that are both motivating and inspiring. I'll be quite pleased if we can reasonably approximate even half of what's out there on this topic.
While I completely agree that we should drive towards open-source with everything we do here (I'm releasing my own software under the MIT license), IMO we don't want to hinder any anons who decide to take their own efforts towards closed, commercial ventures. I don't particularly agree with them, but I also recognize the power money has for motivating people to be inventive. If they contribute even the slightest things towards /robowaifu/s efforts then we can be grateful for that at the least. My own vision for this project is definitely in line with your stated end-game: "...a fully open source and home-buildable robot waifu available to the masses".
The hardware is an issue yes. But tbh, I don't think the problems with bipedalism for robowaifus will remain untenable for amateurs forever. Certainly you won't have to wait until you're 60 anon. Mobile Inverted Pendulum software is out there already and the issues of mechanical and kinematic coordination for bipedal locomotion are becoming more and more well-understood. Surely some autistic mechanical & software engineers will get to the bottom of an effective solution for it before too much longer. There are certainly many motivations for them doing so. My only hope is that the essentials will be open and freely available to us all to create our own robowaifus with.
However, I also entirely agree that we should take an incremental approach and achieve what we can right now, with what we have. I think most so-called engineering & math 'breakthroughs' came through this step-wise method, and most probably took years before fruition. And remember Sir Isaac Newton's famous quote.
Yes, we should be trying to achieve a VR/Visual waifu together now. For digital assets creation, Blender 2.8 is out now and has become a really a powerful tool. An anon mentioned a couple of major ecchi games that could be helpful in this area in the Meta thread. And the list of everything else you mentioned has at least one thread here on /robowaifu/ (often more than one). And it's getting easier and easier everyday to both imagine and to accomplish things like mocap and virtual assistants using cheap, commodity hardware and (often) open software.
And yes, we should be working together on coordinating and collaborating on all these things. /robowaifu/ is a decent enough platform to at least begin to accomplish this. And Torvald's git, and repo sites like gitlab & gitgud, etc., are already pretty well-established at successfully enabling distributed teams to work together on software projects. Trello is a great (botnet) tool for coordinating practically anything in a more freeform way.
So I think there's hope for success. But it will take each individual here to stop lurking and become personally motivated to put in the hard effort of their own to move us all forward. Anons who feel motivated to lead should do so, and help motivate the others forward as well. Personally, I'm learning to program. I'm learning electronics basics. I've learned Maya and I'm dabbling with Blender. I'm trying to gitgud at maths and to dabble into TensorFlow and Deep Learning. All these things took me shittons of effort and time to pick up, and I definitely have a ways to go yet. But I'm trying.
Honestly, each of us will have to be serious about the idea and be willing to put in a lot of hard work. I think we can do it together anon. I'm always hopeful.
BTW thanks for the quality OP, Anon.