if you "shipped" them somewhere, they'd be in an asylum/shelter/jail facility which is set up to handle them, not in a back yard, not downtown, not IN THE STREETS.
Sure, I suggested local jails upthread. You as thread parent suggested "outside the city limits". SF is a "city and county", so it's not possible to have a local jail outside city limits. You're going to have to bribe some other county to take care of the homeless you've charged with crimes. That's not going to be cheap!
It's not cheap even if you manage to get all your jails built in Sunset or some other backwater. Jail is expensive, and the homeless have no official salaries to garnish so you can't use the Ferguson method. Besides which, there's no way the state is going to take any convicted public poopers off your hands to house in their expensive prisons, so you're going to have to keep these criminals jailed for their entire sentence.
Wouldn't it be easier to open some public restrooms?
Some people "just want to watch the world burn" and will mess up anything you try to give them, and those people need law enforcement to stop them, because they won't stop themselves. It's unrealistic to think you can solve the problem with only the carrot.
Shitting is not a voluntary activity. Public restrooms could only be considered "carrots" if they included additional amenities beyond the most basic requirements of elimination and hygiene. Is anyone suggesting that?
There are public restrooms in every Starbucks (and please don't tell me there are not enough Starbucks in SF), it's their policy to let homeless and everyone else to use their restrooms without purchase. Not to mention actual public restrooms, restrooms in shops, parks, porta-potties etc. If there had been long lines of people trying to use those we could agree that there is not enough and we should open more. But it is not the case, is it?