I concur with the others. Fantasy is one thing. Sure it would be an ideal to be so under some ones control that you even have your bodily functions under your masters control.
But the reality would be walking around with a bag attached to your hip that your wast would be collected into. I have had friends who have had colostomy were the colon is removed and you just empty into a bag. Sounds like fun? No. While I am not a wheel chair driver I work with other's and have contact with these unfortunate individual's that do not have any control of there bodies. No arms no leg's they can not control there wast either. No one would want this and for many of them they have a do not resuscitate order in place.
You want nothing to do with this. Sure you are your owners property but your first duty is to protect your self for your owners pleasure. Some times you have to protect your self from your owners own stupidity.
Compromise offer to wear a but plug for an extended time. But do not ever do some thing as undo able as this.