There seems to be a little bit of interest, here, so here goes ...
... here's the basic frame:

Just a basic "ladder" frame with a 24" long 2" receiver tube welded in between the 1st & 2nd cross-members ... the removable tongue is 2"x2"x.125"x60" long ... it is "pinned-in" here with two 1/2" Grade-8 bolts, but to be easily removable you can use two standard 1/2" hitch-pins. If you look closely, you can just see the two studs under the forward part of the receiver tube where a fold-away jack-stand mounts so the front oF the trailer can be supported when the tongue is removed.
Here's a pic of my personal trailer, LB#23, right after I brought it home from its original owner:

You can just see the fold-away tongue-stand, but also you can see the swing-away castered tongue-jack. I have not kept track of the total miles I've pulled this teardrop over the last 6+ years, but in those same years I've logged some 103,000 miles on my Saturn Wagon, and easily half of those miles were pulling this teardrop ... from dead-empty as you see here, to fully-loaded ice-chest on the tongue along with fully-loaded roof rack & basket and a chuck-full galley. I'm not a fan of tongue-weights (for teardrops) of much over 100#, but I can assure you that this one has been well over 200# on many occasions, and on all manner of roads, and it has never shown any signs of stress, let alone failure.
I've built at least 6 teardrops using this type of frame, including a 10' model that has cross-crossed this country at least four times (not including the 6,300 miles
I put on it in 2005 when I went out to the 1st ITG and then extended the trip another three weeks), and a utility trailer that I use for
everything, including hauling a couple of thousand pounds of building materials over a couple of thousand miles!
I can imagine there could be the possibility of a liability issue if a major Mfg. were to offer this kind of chassis, but I can see no reason for the typical home-builder (or even small mfg.) to come up with and use something similar and not have any problems ... just like me. I'm sure I'll get some naysayers, but my record speaks for itself.
Good luck, and as always ...
CHEERS!