It's more of a specification problem: solo are generally a good tool for, well, soloing a track while you're doing a mix or whatever of the kind. Once you've automated your solos, how are you supposed to use the solo-as-diagnosis feature?
So I guess there are use cases where it still would be desirable to have something looking like solo-automation, for instance, to record a perfomance featuring soloing. But that needs to not come in the way of people using solo as solo switches while mixing/listening to their track.
at first it looks like an argument but i think it's not that important. people do tons of weird stuff during their mixing process - like equalizing. there is automation for that too, isn't it? i suppose soloing is a little bit different but not too much... now that i think about it: theres the function for exclusive soloing what could be used during the mixing of a track that has solo automation.
thing is: if you perform you definitely want to use solo buttons for breaks etc because they are straightforward (there might already exist some workaraounds that arent straightforward) and if you listen to the recorded perfomance (i actually build tracks from the session view - the jam way of live...) the break is just gone.
thats really lame. and its a pain in the ass.
some people i spoke about it didnt understand it neither, and complaint about it.
so another +2
just would be great to have...