Hi Gary:
I'll answer the easier questions and leave the harder ones to Michael.

The GL Groups list is fixed, though there have been suggestions to make it possible to add new ones. I would be surprised if that was high on the R&D priority list.
But the other thing to know is that it's not mandatory to assign each GL account to a Group. Therefore probably the majority of charts of accounts currently aren't using Groups.
I would say that if you need to distinguish account types for Dynac's purposes, you could insist that accounts be linked to Groups. It's only a 15 minute exercise if the COA is well-structured.