independently barlined staves in a StaffGroup?

[Jeremy Joseph Boor]

In a StaffGroup using mensurstriche barlines, I would like
to be able to place (dotted) barlines independently in the
separate staves without having to hide them every time in
the other staves.  It would look something like this:


       _______________________________
Soprano| :   :      :   :      :  :  ||
       |    |    |    |    |    |    ||
Alto   |    :  :         :   :     : ||
       |    |    |    |    |    |    ||
Tenor  |  :       :    : :    :    : ||
       |    |    |    |    |    |    ||
Bass   |  :    :   :    :        :   ||
        -------------------------------


(if that helps at all).

I want the whole sytem timed regularly, with barlines
between staves, but each staff should act as if it 
were under \set Score.timing = ##f, and without the
arbitrarily placed (dotted) barlines showing up in the all
the staves nor between them when I put them in one staff.

Any ideas?

Many thanks.