Implement a taxonomy only resource group type

We organise our resources into groups that are our business services. We also use the device groups to define a hierarchy of the business service groups, so we have device groups that are used as taxonomy groups, simply to do nothing other than organise our hierarchy, and will never have any resources assigned to them.  However, it's possible to accidentally drag and drop resrouces into these 'taxonomy' groups, or for a user to mistakenly select one of these groups.

What I would like is to have a special resource group type which is used for defining resource group taxonomy only and cannot have resources assigned to it.  The group's icon should also be different so that it is easy to know that this is a taxonomy group.