Your architect, principal engineer etc. (one spot-on job title I've seen is "product architect"), who in turn talks to the senior management.
Basically an engineer with a talent and experience for building products rather than a manager with superficial understanding of engineering. I think the most ambitious teams have someone like this on top - or at least around
I've had your type of product owner, but I've also had a product owner that was an ex-staff engineer. Companies should hire ex-engineer product owners, not strictly people-manager product owners.
Technical background doesn't always help in my experience - it's just a different role. Creating great product requires deep technical expertise to understand where the cutting edge is, vision to understand how it can be expanded and business expertise to understand what makes sense economically. It's just not a manager's job, you can't perform it by collecting customer requirements in a spreadsheet.
