Bending goes both downwards and upwards... No way to do this with either a pedal OR aftertouch.
Plus, if you have ever seen a graphical piano roll of standard playing, you'll notice that, if you play with the full dynamics the keyboard allows you, you will ALWAYS get aftertouch messages whether you want them or not. If these are tied to pitch, you are going to get all kinds of bends where you don't want them.
An arranger is just a tool. What matters is what you build with it..!