Model got his two hundred thousand men and extra panzer divisions? That was allegedly his demand to even attempt to hold the city.
Its fairly easy to have the Germans demolish it on the way out and they did shell and bomb it out of spite but the garrison was inadequate and the field forces busy getting sucked into a number of meat grinder battles followed by a rapid rout back to Germany.
A prolonged battle in the city itself requires them to have forces that they just did not have to hand. If they do seriously concentrate in the city the Allies probably just sweep around it which pretty much seemed to be the plan before De Gaulle and resistance forced the issue.
I think the end result is Paris takes a beating but otherwise not much else.