I think the car haulers are a good idea. IMO $125/day and $200/weekend is reasonable. Also a good idea to offer a winch for $50, straps for $25, etc.
The enclosed trailers will get torn up in a hurry. It’s not difficult to rip off a rear corner on one going into a driveway, and I have a hole through the front stone shield on mine I have no idea where it came from. Nobody but me has ever driven it. Not a huge deal though if they cost $2,000 new and you rent them out for 10 weekends at $200 a pop.
Most newer trucks have factory brake controllers, and there are some new wireless ones that plug into the 7 way you could rent.
An easy way to get around the “can’t drive a trailer hurdle” is making your rental area a bit of a bitch to get out of. I pull a trailer so much I cranked the steering wheel the wrong way without one this morning backing out of my driveway and almost hit the fence.