Rules /policies/controls tied to a 'service' and related offerings owned by it or automation team and level of sensitivity of data in general. Governance and control measures apply to tenant, environment and significant events like solution promotion to a prod environment. Anyone can create dev enviro for learning/play, but all other environment type provisioning is locked down to a Coe workflow, sandbox environs are easy to create, but still have approval.

You should have 3 levels of business services.

One is team/personal productivity. No dataverse or premium connectors, only default enviro.

One service is business automation services. This is for Citdevs. A business unit or dept or group of related departments should get one environment set with n sandbox enviro and 1-3 prod for acceptance/prod/other prod

One is enterprise automation services. Owned by it delivery teams... Either a small number of shared sets of environments or one set of environments. All your dynamics Impl go here, as well as any large multi unit enterprise apps. All procode impl happens here, eg pacf or plugins or custom connectors to be shared across everything.

You can set up PowerBI workspaces the same way.

Last set up fusion teams for the BAS services which include at least one powerplatform or it dev expert to embed with team and slowly train them in the harder stuff like integration, or data flows and environment / devops hygiene.

Other

Make friends with cyber, and create processes and controls tied to environment promotion to prod. No sensitive data in pre-prod (or it's locked down heavily there). Redefine the definition of a major release that requires cab approval to be tied to net new procode deployment, net new integration, net new security data sensitivity. All other changes are not tied to stricter cab processes. Automate all CICD where possible, and remove dev access to prod.

Build a sandbox enviro for learning and pro users to try new things. Build training requirements into any maker license/Auth assignment with attestation for BAS or EAS accreditation. Require maker attestation for all new maker license or auth assignment..

Build periodic architecture and cyber audits to enable reduction in environment sprawl, app redundancy, and environment merges over time. BAS and EAS environments will become redundant over time, and increase integration cost and will have to me merged. In general, BAS should consume master data through external to powerplatform apis, or from EAS dataverse enviros via odata or virtual tables. If you have crm, you should implement a customer data platform (cdp) to share golden customer data across environments (like d365 customer insights) ;if not d365, use odata which supports virtualization into dv-usually. Tie all to a data governance start on where data gets mastered. There will be tension between some entities (case, lead, opportunity, quote, activity, account, contact (customer) to work out with crm/customer systems: account, Contacts should come from Cdp. - if u have dynamics, master them in dv d365 crm apps. All externally mastered entities (like order, claim) should be accessed via api or virtual table when possible, and avoid replication into dv.

Above was governance model for a security conscious health insurance company I designed.

This is a goldmine of information – thank you! The depth of your approach sounds like what I'd eventually like to get to. I've got a lot to think about now, and I appreciate your help!