Any chance this (syncing transports via Link or otherwise) has been added or is in the process? I've been on the fence about AF since early last year but this is one big reason I haven't pulled the trigger. Ableton's browser is nearly useless if you have a large audio library, but anything external would lose the ability to audition in sync which is just a complete buzzkiller.
I love Link personally and use it from time to time with iOS devices. I think it would be a great way to address this need.