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It is my understanding that there are or have been several earth-viewing
*brothers* of Hubble, built by the same manufacturer, but for a
different customer.  Aparently several of Hubble's non-optical problems
are well known but can't be talked about.
 
As far as anti-optics -- I think that the major optics could be the same,
but that the minor optics and sensors would have to be different.  Of
course, there are major problems in pointing to a new target twice in
each orbit; if you think that a shutter mirror causes vibrations and
needs to be locked up to take a **really good** picture, just think about
the vibrations caused by slewing to a new orientation, whether it is
done by jets or reaction wheels.