Not totally "off the shelf" components', but close. Brackets are uni-strut fasteners from Home Depot (pre drilled/zinc coated, .250 x 1.00 flat bar and angle). 1/2" bolts/nuts/washers from the local Fastenal supplier and the short piece of grip-strut was a drop from the local steel supplier. All in, the multi-purpose tongue step/genset platform cost me $30. If I would have had to purchase the usual minimum length (10') of grip-strut, the project would have been much more expensive. I isolated the brackets/bolts from contacting the AL OTT frame with simple spacers made from some HDPE sheet stock and PEX tubing I had lying around from previous projects.
Depending on what I carry on the rack, the tail gate clears as long as the truck/trailer is straightened out. But, I use an extended length hitch. No Anderson stuff required. TV is a Ford F350 and the tailgate is higher above the ground than most rigs.
I usually have a short Pelican case, through bolted to the platform, caring blocks/gloves/misc stuff or don't care anything on the tongue. I prefer to leave it open and use it as a step when transitioning from the bed of the truck to the ground. Most of the crap I think I need to drag along is in the bed of the truck in Pelican cases or stored in the rear passenger area.
I originally intended to re-purpose a Pelican 1660 case for a tongue box...didn't like the look.
I purchased the propane powered genset specifically for the OTT and have yet to use it, except in testing. Solar meets most of our boon-docking/back country trip needs. I plan to fabricated a plate for the genset which will allow me to directly attach and lock it to the tongue platform. For now, a couple of Mac's straps do the job. A simple draw string bag covers the genset during travels. Tie down straps
I had a detailed installation posted but it, along with other postings, disappeared after the website "upgrade".