Question
Is there anyway to remove a managed package (Action Plans) that was installed into a managed package dev (My Managed Package) org after being released? Assuming yes, are there any dangers or complications with doing this? Again assuming yes, once an installed org upgrades to the newer version of our managed package (My Managed Package) would we be able to remove the other managed package (Action Plans)?
Background
I'm working on a managed package that includes the Action Plans managed package module. We now need to customize Action Plans and to do this need to switch to the unmanaged version. We don't extend the package, just have buttons from it on some page layouts which we can remove. Seems like this may be possible, but could have some potential dangers. Since managed packages aren't so undo friendly and don't have sandboxes I'm hoping someone out there may have actually done this and be able to provide some real world info.
Best Answer
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.