I think the idea here is to take the current Tempo View and simply display it in the Track View - so clips would not change any more so than they do today.  Plus, audio-wise, only Groove Clips change their duration depending on tempo.
 

Nice ideas all over here.. :)

I agree that the tempo view is outdated. It is possible to draw in tempos, but it's not very convenient. To get it where you want you have to zoom in a lot.
 
It would be awesome if it worked more like an ordinary automation line with nodes and such :)

I absolutely support the idea of being able to input automation for this during playback, using a foot pedal or somesuch.  I use the tempo map but find it a bit unwieldy when I want a rit. or accel to sound natural.  Having it create an automation line that superimposes in the track view would also be helpful.