I think about this as well, and this is what I came up with. (Feel free to disagree)
Product Manager oversees multiple products in a suite and a PO manages one of them. The PM coordinates PI planning with the POs on the shared FY vision and roadmap.
Product Designer ensures the unified experience is consistent between products within the suite and tracks the UX maturity score and SUS score. Has vision on the design system, workflows, accessibility score and coordinates with Dev manager on UAT.
PM is focused on collective health of the suite for business success. Monitors dependency report between ALL shared services. Makes sure each PO is tracking release management with QA ahead of code freeze for client presentation.
PO is focused on delivering specific commitments and releases. Monitors dependencies specific to their workflow, but nothing else. Relies on PM to coordinate with other POs.
PD coordinates with UX Researchers and Designers specific to each product. Ensures UX is two Sprints ahead of Dev for usability testing and prototype handoff. Maintains business vision with PM and facilitates product demos for stakeholder feedback.
Everyone is aligned to the specific fix version, so no one goes outside of operational parameters. Even though UX might come up with an innovative solution, they can’t deviate outside of the technical debt of the Dev team without presenting it and submitting a change request form on the feature release so everyone can adjust.
No one works in a vacuum. Transparency is paramount. If there are problems, an impact report has to be submitted for executive review.
Everyone has to operate within their budget envelope.
Finance team works with Sales for closed loop analysis to measure business impact on ROI.
Project Manager works with PEO to make sure everyone is tracking correctly and in the correct fix version.
Dependency Reporting is vital for the roadmap.
Reporting is broken up based on Strategic Leadership. (1.) Executive team looks at budget. (2.) Product team looks at dependency report. (3.) Sales team monitors planned release date and participates as SMEs and assists with usability recruitment.
Good luck and I hope this POV helped!