It sounds like for your case, the answer to "Do I have a technical problem that's legitimately unusual and faced by very few other businesses?" is "yes", so you

It sounds like for your case, the answer to "Do I have a technical problem that's legitimately unusual and faced by very few other businesses?" is "yes", so you probably have to build it. The point is to only build things that are necessary for your product, not to avoid building anything.