>Lift, by definition, is a vortices. The trick is to get the lift as cheaply as possible

limit the transverse flow and you limit the induced drag of sucking a vortice along in the wing tips wake. This is exactly the reason ground effect vehicles will pull lift coefficients (calculated by their much slower stall speed) of 2.2 from a foil that has a coefficient of 1.2 in free space. We did some work on the Soviet Ground Effect test bed ESKA 1, a double reverse delta planform of the Lippisch type, (look it up) The reasoning is similar but the amount of taper on ESKA 1 is beyond extreme.

>There is a reason they put the tail up there and it wasn't to increase the weight and complexity of the wing I am sure.

its the same reason I am discussing with a double reverse sweep tail, just in this case by its position it is tending to suck air from the tip

their reasoning is likely to be, we have to have it anyway, what shall we do with it. There is an obvious attraction to manipulating the wake off the wing tip. It isnt about exciting air, it is about keeping the flow laminar as long as possible across the foil

the reason we don't see severe tapers on aircraft is because they need to maintain aileron effectiveness in a stall. A severe taper will cause the stall to propagate at the narrowest chord first, ailerons stalled have no authority and the aircraft in such a stall will snap spin with catastrophic effects.

At the end of the day I am quite sure an endplate will provide the most satisfactory fix, and it wont weigh more than a few pounds at most.