Towing...B+E clarification...Advice

[nominous]

its all retrofitted to the car.. they actually modify the sub frame of the vehicle and add hitching points for the A frame

Cheers for the link. That wouldn't work quite for me, I'd want different attachment points that a large lump of steel behind the bumper.

and no not so easy to "throw something together", the trailer needs to be verified and tested, all their work is Emarked and certified, it would be illegal without it as the trailer would be a new construction

Trailer? You mean the A frame part ?
I'll go read the regs. I don't think there is a problem when it comes to trailers as far as making your own. For a A frame, does this mean it's treated differently?
So the DIY approach is not allowed - we be surprised.
Since hydro or electric control over the towed vehicle is allowed, it's fairly easy to build something to control it. Including the required vacuum pump.