Sorry to revive this thread, but having gone through the aspect ratio thingy recently, I feel that while it is very nice to be able to have custom render scripts, the default one should still accommodate some basic options.
Obvious things like scale XY, scaleX, scaleY and noscale could be user choices in the project settings right under the display resolution.
I think that for beginners it would be more accessible, while expert users could still change the render script.
my 2 cents =)