Actually they ARE intended for highway use, they're just not common on lighter trailers. Most Fed-EX and UPS trucks towing doubles are towing off a pintle... And most any equipment trailer behind a dump truck is pintle as well.
I have a few military trailers with pintle hitches. If you're towing them with the setup above, which is a combination hitch, then they are a bit sloppy, and with a lightly loaded trailer, you'll get some commotion out of the hitch if the going gets rough, particularly if the trailer is empty. If I use an actual pintle hitch instead of the combo, there is little noise or detectable slop, even though there's obviously more than a ball... Once you load the trailer, the tongue weight keeps it quiet, for the most part. At least when towing down the road.
The plus of a ball hitch is that it's relatively quiet even when the trailer is empty, with little tongue weight.
The plus of the pintle is that it will handle quite a bit more tongue weight, it's less fussy to hook up, and as I see it, your trailer is less likely to disappear, or get borrowed all the time.
If I was going to build a heavy trailer that wasn't a gooseneck, I'd consider putting a pintle on it at this point. SO much easier to hook up, since you just back up till it goes bump, and then lower it and flip the latch down. If you're close enough that it doesn't shift to the side when you bump it, you're close enough to drop it on the hook. If the trailer shifts slightly to one side or the other as you bump it, then you know which way to reposition without even getting out of the truck.
Just relaying my experience...