After a quick search, I believe your Frontier is body-on-frame, with a payload somewhere close to 1500 lbs depending on exact equipment. This suggests that your rear suspension will be more than capable of supporting hitch weights in the 500-600 lb range. Class III hitch receivers offered for the 2007 Frontier can carry 750 or 800 lbs of hitch weight if WD is used, or generally somewhat less without WD. The frame of the pickup will handle this weight fine, too. Do not worry about the hitch weight on that KZ, it won't be a problem. I know, most of the time a hitch receiver will be rated to take 10% of its tow capacity as hitch weight: 3500/350, 5000/500, etc. But your pickup is an exception. So is my current Lexus GX, which (with the OEM receiver) tows 6500 lbs but can take over 900 lbs of hitch weight... the numbers are stamped right on it from the factory.
I had a KZ Escape 14RB for 3.5 years and towed with a 2008 Highlander, 5000/500 rating. My KZ was 2700 lbs and about 370 on the tongue, loaded. No issues... well, other than the Curt receiver which broke apart, but that wasn't the trailer's fault.
I will say that a Scamp, Casita, Parkliner, or Li'l Snoozy will have less wind resistance than the KZ because they're more rounded and have less frontal area. Of those brands, only Parkliner is being sold via dealers; the rest are factory direct. I understand your concern about warranty work, however most interior appliances and such are standard brand names that carry their own mfr warranties and can be serviced by any RV dealer, and the trailer mfrs have a reimbursement policy for repairing other things when it isn't practical to return to the factory. Body repair can be done by a fiberglass repair shop; I have one of these molded fiberglass trailers and I took it to a boat place to fix some cracks around the doorway.
Be aware that the width spec on that R-Pod includes the outrigger wheels, which produce relatively little drag. The body itself is not that wide (6.5' maybe?), so it should actually have less frontal area than the KZ.
The 4-cylinder engine will need some high RPMs to tow up hills, but if you don't mind listening to it wind up and you don't expect to charge up grades at full highway speed, your pickup should do well enough. Just plan on driving 55-60 mph on the flats.
I once towed a 13' Burro (the molded FG egg TT) on a 2000 mile vacation with an '84 Dodge Omni 2.2L, stick shift. That was less than 100 HP IIRC. It struggled to maintain 55 mph. But you have about 1.5 times as much HP and probably way more torque than that old Omni.
Go for it! :)