I disagree the macro and generics are related.
If you want that kind of syntax you will need another character for generics or you will need to change the macro invocation. For instance Option`Rc`RefCell`Node would seem pretty clean to me, far less heavy than exclamation point or brackets, while I don't think the issue is important enough to introduce a new syntax at this point.
I did that kind of thing long ago too, while my incontrovertibly correct opinion does not exactly match yours 