Keep in mind folks, the OP is talking about a 2019+ Ranger and not one of our original models. It's bigger, heavier, and has more power. Granted, it's not an F-150 but what he is asking about is within the manufacturer's limitations. Now, whether U-Haul agrees with that or not may be another story.
For what it's worth
@Blmpkn, it's probably best to give them a call instead of us beating a dead horse about what they may or may not allow. If they tell you no, then it sounds like your Uncle's trailer looks like the next best option. It might even be better since I'm sure it's brake equipped. If you don't have the brake module already, there is at least one available from Ford now that is plug and play. No wire cutting or anything from what I understand. Aftermarket, if they are even offering anything yet, is more than likely going to require cutting and splicing.
I just did a quick look. The Ford controller is pricey and you may need a pig tail since the wires for the controller might not have a plug installed. There were a couple models offered on eTrailer that were pricey as well the
looked like they are meant to be plug and play. Then there was your standard $80 some dollar units that you would have to slice and dice to install them.
In the end, it depends on how bad you want to be able to use trailer brakes and if you think you will use the module enough for it to be worth the cost. Me personally, I would want the trailer brakes functional at the weights you are looking at.