Option to allow creating subgroups only "inside" parent group

Let's consider following situation: I got two group types, Project and Project Team. I want to allow the creation of Project Teams ONLY INSIDE Projects. Same Project Team can be part of multiple Projects (obviously this ggroup module allows it, unlike the subgroup module), but Project Team should never exist outside of a Project.

Currently with this module, it is possible to create Project Teams directly, without them being subgroups of certain Project. I can't see any way of preventing it either, at least not without some additional modules (for example "URL Restriction By Role"). I was just wondering if this would be a feature that could/should be added to this module?

I do remember the Subgroup (subgroup) module does this automatically, it actually completely removes the subgroup type even from the Group UI (/group/add) so it's not even an option to add a subgroup directly without parent group context.