Limited region size is still my biggest complain about Simcity... Offline was never a big problem for me.
How big do you need a region to be?
A twelve-city region became an opinion with Update 9 - and that is TOO big, for me, that is. (My biggest private regions are eight cities large - Sandbox or otherwise. And that is before offline came into play.)
Most of the complaints are about CITY size - not region size. (In fact, regions aren't even an option in previous versions of Sim City - each city existed standalone and separated.)
Because of offline, I can now actually do more realistic regional models of real small towns and cities (suburbs, for example).