* Are the core developers interested in having multi-site support in the update process? (I mean, why work on something just to have it go nowhere, right?)
yes . multi-site is very much a supported feature. so is the update system. their combination needs to be supproted as well.
* What do you think is a better/more workable/more Drupal-like approach:
a) put an option in the process that the user can select (in update_selection_page(), I guess) that tells the system to update all tables in the database, not just those for the present site.
b) an option for the user to say whether to update the shared tables or not. This way, the user will update each site in each site's interface, but the user will only select the shared table run one time.
c) other ideas?
the only solution that is even somewhat workable in my small brain is to warn the user and then upgrade all the sites at once. i think thats the deal with multi-site. you need to do separate sites if you want them to be on different versions. if you can think of more flexible solutions, thats great.