I don't think it is really necessary to create specific account types,
this seems like it would be difficult to maintain (constantly changing).
I think the user should be able to create "ALL" types, the specific
types already existing in the system are good examples (and should be
kept), but they should be treated more like templates an not de facto.
Here is my suggestion:
Allow the user to create their own fields, label them and use them to do
whatever is needed. The fields should also contain an attribute that
allows whether the field should be copied or not.
I really like this tool and would like to keep using it, and hopefully
improving it as well.