>What I'd like to see is a global or shared datassession that could be accessed from within many private datasessions. That way system tables could be opened and referenced there and still have the benefit of private datasessions for specific type application data. Closing the private datasession would only close those tables, leaving the "shared" session open.

Well datasession id 1 is the "global" session, and sometimes I will simply create a cursor in that session from within a private datasession by using "set datasession " command. Any tables required are simply "use again" so there's no apparent speed penalty.
eg say we are in datasession id 5

set datasession to 1
lUsed= used('mytable')
select * from mytable where <somecondition> into cursor mycursor
if ! lused
  use in mytable
endif
set datasession to 5

In reality I'd use a few properties to do this more neatly; but you get the idea?