Group Policy Management Tools

Solution 1:

AGPM does much of that - it's a Microsoft tool that vendors like Microfocus leveraged off. It does all the versioning, check-in/check-out, approvals, roll-backs etc. It's not highly sophisicated, but it does the job.

https://docs.microsoft.com/en-us/microsoft-desktop-optimization-pack/agpm/advanced-group-policy-management-40

The main drawback in a multi-forest environment is that it's a per-forest tool. You need to import and export GPOs between forests if required (such as between Test and Production forests): https://docs.microsoft.com/en-us/microsoft-desktop-optimization-pack/agpm/using-a-test-environment).

Obviously exporting and transferring files can be scripted to some degree, but fundamentally, there's no single management point for multiple forests, so you'd need an AGPM instance for each.