#3 is smart... I should have thought about that before lopping of the shock mounts on my Sterling.
#2 is only partially true -- you don't NEED the center tone ring to restore ABS -- you just need something that sends the right amount of tones that can indicate identify that your rear wheels are locked up while your front wheels are spinning -- as that's what the ABS responds to.
Sure there is some difficulty in adapting an RSC axle to an non-RSC van - but it is possible and IMO is easier than installing an e-locker and re-meshing the gears.
Plus -- there is some evidence that the magnetic field from an engaged e-locker can overwhelm the ABS tone ring/sensor combo in the rear differential. There was one gentleman who said on his rig -- when he triggered an e-locker, he lost his speedometer. I'll try and find documentation of it -- but I forget exactly what forum it was on.
I assume this isn't widespread -- but it seems feasible to me.
I can manufacture a tone ring you can mount to your output flange on your transfer case if you want.
I've actually thought about making a kit for the NP271 and common axle ratios -- tone ring for the output flange and mounting hardware for the sensor - but haven't gotten around to it yet -- if you're interested -- I could use a test dummy