its possible. i don't have to make that many changes to make it worthwhile for me to do it. What I generally do that, is write my lists up in notepad, and then paste them in.
I would probably think about this:
storing existing lists. update them, and serialize the access list name (access list outside1.11, etc).
connecting to the pix
entering in new list (it is a new list because its name is incremented serially)
change the access group statement to the new list name
then clear out old access list name
this way, there is minimal downtime between the old list and new list being in place, and you avoid any hijinx for editing a list that it is production
