What ever it is, please keep in mind your audience. They've been using WAU and Ace plugins for awhile and they just want to get back to playing WoW with their favorite addons.
To be honest, you and I aren't their audience. The real WowAce audience is and always has been the addon developers, not your run-of-the-mill end user.
We were always meant to use the established download sites like curse or WowInterface. Coming to depend on WAU and files.wowace.com was a mistake on all sides. The users are just going to have to come to grips with the fact that the situation became untenable, and the change was for the benefit of the devs, not us.