Although this thread is old, I haven't seen any additional information about this point.

The game doesn't seem to recognize the victory condition take_regions XX if it has not the condition hold_regions Region1 Region2 in the line above.

In the short campaign I haven't tried any condition different from outlive_factions. Does anybody know if it is possible to put the same system hold_regions + take_regions as in the long campaign?

Perhaps this is known by most of modders, but just in case...
you can change from long to short provincial campaign by selecting the type of campaign for imperial campaign, going back to the main menu and selecting then the provincial campaign.