You can install anything up to 2" bolt on. Some require removing parts of the bumper plastic and then reinstall it after the hitch. The total load rating of a v is about 950 pounds which includes passengers. Toyota does not recommend towing due to the suspension, rear hub bearings and brakes. I used one for things like bike carriers but others have pulled trailers. I know the rear hubs can't take much load but wear generally results in howling rather than hubs getting loose. A heavy load will also force more regen, lower mpg and could aggravate an already fragile gen3 engine. Going down long mountain grades could be a problem as increased regen would fill the hv battery and switch to engine and friction braking alone. So if the loads will be light you may be ok.
In my gen 2 I hauled 2600 lbs of gravel over hilly roads, when I moved from state to state 8 years ago I hauled 2000 lbs 700 miles, both with a 600 lbs single axle aluminum utility trailer. Twice I've towed 2800 lb 280ZX's with a tow bar over 100 miles. pic related is a load of wood from Home Depot to build a storage shed Breaking The Prius Towing Convention | PriusChat
IMHO; you can do anything you want - It's a free country. The real question is should you. If you get into an accident and/or injure someone; you're going to have to explain the extra load and the other sides attorney will probably note that Toyota does not recommend towing. I've seen idiots rig up leaf-spring U-bolt clamps to mount a 2" hitch onto uni-body cars. Wouldn't want to be near them on a highway. Just my two cents....
