Personally I very much agree that
- Clicking on a tile with a specific notification doesn't take you to that thing the notification represents. Instead it launches the app and you have to dig around the app to find the thing you were notified about (Facebook is a prime example). I find that very frustrating as that's what I'm used to on my Android phone.
is a huge problem with the current implementation of Start and live tiles. So I think a reliable way to deep link into the specific information a tile update represents would be very welcome.
OTOH I'm not sure the start screen would be a good place for more involved interactions with an app. The objections RealBBoy and magicalclick raised, that it would complicate interaction with Start and present developers a dilemma of where to implement features or require them to implement the features twice, are pretty salient I think.
So personally I'd prefer if interactions with tiles were kept focused on (1) dynamic deep links (e.g., click on a specific email out of several in a large tile and open that email directly) and (2) quick actions involving no more than 1-2 user interactions, the sort of thing you might see in a taskbar thumbnail (e.g. play/pause for music) or an Android notification (e.g. quick delete for an email). Whereas something more involved, like replying to an email, would be reserved for the app itself.