I think a it'd be pretty cool if when you select a few layers and then create a null (ctrl+alt+shift+y) it'd auto parent the layers you have selected.
I think it could save some time.
A potential problem I can see is the null being in the middle of the comp say if you wanted to scale. could be fixed by having the null being created in the median point of the multiple layers.
And yes I know you can parent after the fact you've created the null before everyone piles on haha