For my tailgate/trailer leveler jack problem and to avoid spending the welding and application time (and money), I believe I will go with the solution of using an extension bar. If I buy one of the bars shown below, drill another hole in the hitch mounting area (to make the bar reach adjustable) and weld a 3/4 to 1" bar for the ball, it will solve my problems and not require any work on the trailer.
Raw Bar

Then weld a ball mounting plate like this one. It also bring the ball height up a bit hopefully to offset the leverage result of lowering the truck hitch height result.
And just to satisfy my paranoid fears, drill a hole through the plate and bar and add a heavy duty nut and bolt.

Thanks razorback for bringing this concept back into my thought process.