There's issues beyond crashes with the launcher's downloader, including the fact that it's still strictly handled through an out-of-game application that not everybody uses. To switch from the Marathon server to the AOW server, a user has to exit their game client and start again. There's a reason I am still planning to replace this mechanism entirely (though I've admittedly been quite inactive lately).
Also, Thommy's version of City is extremely poor and shouldn't at any point be considered a substitute for a proper finished version of City. Many assets required for City do not yet exist, and still need to be added. Adding his version of City will just leave a bad taste in people's mouths for those who have been long anticipating City, including myself.