ArabianGrace, my internet don't want to load your pic, so I can't see how big your horse is. I live in a country where every Dick, Tom and Harry own two horses and a cart and the "bridles" on those horses vary from a wire halter to something made from conveyer belting. My first question would be: How big is the horse(s) you are planning on driving in the sidepull? If you're talking a team of full sized draft horses - Yikes! That I don't think would be a very good idea, but if were talking one or two minis pulling a little cart I suppose it might be doable.
The horses would have to be VERY well trained. But I suppose Theoretically if one person can ride their horse in a neck rope, who says you can't drive your horse in a sidepull? Provided of course you take all due safety precautions.