Right now we are deep into the days of cloud. It's hard to imagine people buying servers! So it's definitely hard to see what role OCP might fit into, with that perspective.
It also feels somewhat like you have your ask inverted:
> I'm interested in how you could build a business around it.
Around or on top of? OCP is kind of there to make suppliers job much harder; OCP is here to twist arms of people making hardware. OCP exists to remove special sauce, to stop vendors from trying to get competitive advantage. Anyone making hardware generally is under threat from OCP, as a kind of ruthless buyers cartel who know exactly what they want, and who is happy to buy the specified product from anyone.
If you are trying to be further up the stack, OCP is amazing. There's a clear ask, that you and many other buyers are hopefully all asking for. There's systematic design efficiencies throughout; instead of only high end special gear having rack-based power (or mini-me edition: large blade chassis, those chassis requiring tons of extra/expensive metal/backplane), it's just standard, normative design. Higher efficiency and cost-optimizing.
Aside from big obvious racks... there's standardized bios/management interfaces that have become vastly more prevalent. OCP nics show up on a very sizable amount of server gear. The buyers have had no real concerted effort to say what it is they want until now, and OCP is a communication/coordination channel for buyers to figure out what they want. It makes the industry better, and the evidence so far has been great, if slow.
With any hope, we are shifting back to an age where more people & more companies actually run their own hardware. I personally see really amazing progress from places like Kubernetes as a key enabler, a tenable start towards a data-center OS, where open source services like cloudnativepg can begin to emerge & compete with the expensive well-served SaaS world we've become addicted to (beat back some Service as a Software Substitute (SaaSS)).