Better than the nincompoops my landlord sends out to "fix" stuff. Better than trying to get someone to fix anything at all in San Francisco.
The truth is I would rather choose from 100 varied vendors - if prefab were permitted in San Francisco, you would be able to buy it from anyone - than to be forced to endure the shitty alternative of simply unpermitted work, or the kind of work that my lunatic licensed electrician neighbor does, which has burned down just as many walls as in your total hypothetical that has never happened.