Mmmm...As far as I know..
There is no support for this...
I could be wrong though..and completely happy to be wrong...
It would be a interesting feature
You can Scale the layouts....but I don't think resizing is supported during run time...I could be wrong...
If you want to have different Resolutions for Screen sizes you could always have 2 or 3 layouts set to the most common aspect ratios..
but I get the feeling you are not after that idea..
I am pretty sure the layout size needs to be set pre- runtime
It probably is possible
I notice that WIX the online webpage creator/editor can resize layouts in real time...so it must be possible..but I dont think its been covered in C2..
Maybe Ashley could give a better answer?