In my opinion it would not be appropriate to use a batter dispenser to "pipe" macarons.
As you know, constant pressure is necessary to ensure even piping and to control the amount of batter.
The dispenser just "dispense" and I doubt the amount will be the same for all the macaron cookie that it is doing to dispense.
Besides , you will ot be able to see the batter being piped (or in this case dispensed) out, hence difficult to control the shape of your batter (being piped). On top of that, you can't "cut off" the batter to minimize the peak. You'll probably end up with one big mess!
My opinion is to stick to using a piping bag fitted with an appropriate nozzle.