What he said^.
I don't have much experience with wdh setups but what I believe will happen is first you'll crank up the bars to take the 250lbs of tongue weight off. Then any additional weight transfer by putting more tension on the bars will begin to help unload camper weight, at the expense of negative tongue weight and trying to rip the tongue off the hitch.
There's no magic answer to your situation.
Now your concept may work, conceptually with a "trailer" that is really just a short load carrying dolly and a hitch that's designed for significant uplift. Like a booster axle on the back of a mixer truck except with a single point of attachment.