[SalesForce] migrating third party managed and unmanaged package from sandbox to production

Yes we've done this and been successful.

However your correct to be cautious about it though. We've had things go wrong under the hood in the past (typically with more complex dependencies than your describing here though). So long as you're not under major pressure to release Salesforce support have in our experience been able to pick through things for you and sort things out, just be sure not go messing around further if things appear odd.

Uninstalling from Packaging Org. So long as you no longer have any references to it, it will uninstall as normal, even from a packaging org. If however you've made references to it via fields lookups for example, that you cannot remove or edit out from your package, because those have been released you will not be able to break the dependency. This doesn't mean you cannot install the unmanaged version, as this will be in the your packaging org namespace. Its just that it would look a little odd to admins in your subscriber orgs to see the same classes, objects etc from the Action Plan namespace and your package namespace, other than this urglyness that may be tolerable.

Uninstalling from Subscriber Org. This again will be possible once you the subscriber org has upgraded to your new dependency free version of your main package.

Having unmanaged package installation approach in production you can't

• Uninstall the package if it is being referenced by component which is not part of that package
• You can not upgrade unmanaged packages. You will have to uninstall the previous one.
• You cannot overwrite a component which has same API name in production but not part of the package and package also contains the component with same API name.
• In production you don't have enough development controls to resolve the dependencies issues. If package start causing issues you will stuck due to lack of controls.

With changesets above issues don't occurs. Also you can build a single unit of changeset and upgrade it by cloning and adding components.

Packages are good for distribution purpose.