>What are the potential weak links in the chain for robowaifus & their development? Electronics? Software? Materials? All of the above?
The weak links aren't any of the above. Those are all quickly developing at a pace to make robot waifus entirely inevitable, at least technologically. It's external factors, see below.
>Who/what is opposed to robowaifus, and why? Private citizens? Governments? Corporations? All of the above? (again)
Private citizens are opposed to robot waifus. It's only once the technological uncanny valley has been surpassed, and robot waifus become useful in a multitude of ways, and streamline your life, that the average private citizen will accept them. Until then, the main topic of discussion around them will revolve around "sexists trying to replace women, oh no!", and "sexists wanting slaves to do house chores, oh no!".
Governments are opposed to robot waifus, since it lowers the birth rate and causes stagnation in the economy as new consumers are not being born, thus not getting jobs, and thus not buying shit to support the boomers through taxes in the welfare state. Especially true for U.S. or other countries with scammy social security that run on the pyramid scheme system. They may like the technology militarily, but socially it has implications that the government doesn't like. Namely less money.
Corporations want to make money, and while selling next-gen robot waifus would make them money, they have to tread the line carefully, since the risks associated with entering that unstable new market and making yourself the figurehead media and individuals can yell at is risky. And could cost them more in the long run if their product is not good enough to attract a large enough consumer base.
>Presuming the first two points are adequately considered, then what are the likely attack vectors that would be used to harm our robowaifus, their systems, or us?
Obviously hacking, but also restriction of certain technologies (i.e. naming technologies as "military technologies", as the government does for space technology, which would prevent up and comers from innovating in the space). If servos, and high end robotics technology was restricted from private citizens then you would find it very hard to sell robot waifus since the ones that would come out will all suck ass, and open source designs would flounder as the technology required to make them, controller modules, precision servos, etc. is restricted.
>Given the first three, what's to be done? How do we most effectively counter any attacks intentionally targeted against robowaifus, their industries, or us?
Well for the robotwaifus themselves, making them offline in every possible way is a huge deal. Understandably the data the AI may need to function may require high end cloud computing, but if possible, steering away from that and making them as disconnected as possible will help. But almost just as important, ensuring that all robotwaifus don't require a "subscription" service or any other always online DRM is extremely necessary to ensure security of the robotwaifu and of the users investment. All it takes is for a company to backpeddle and start removing features people wanted due to public scrutiny, or for the cloud the robotwaifu uses to go down after a long period of time and suddenly you have a hunk of human-shaped metal that can't move or do anything.
This can also be helped by using open source or freely modable software. This way, the modification, customization, and utility of robotwaifus becomes as decentralized as possible. Sure, a company may be flamed for updating the robotwaifu to respond appropriately to "go back to the kitchen and make me a sandwich", but if users can freely mod their robotwaifu to do anything THEY want, security updates, modifications, and new features could continue to be added even as the company who made the waifu is long gone.