Out of curiosity has any one ever thought about, tried to or adapted the Rubicon Electronic Sway Bar Disconnect to a 4runner?

You can find them on ebay for a reasonable price (less than KDSS). Probably can shop around and get them for 1/2 that.
2007-18 Jeep Wrangler Rubicon Electronic Disconnect Front Sway Bar #52121753AH | eBay

The innards of the assembly are pretty simple (Youtube). Two splines on each end of the sway bar pieces slide into a matching splined sleeve.The sleeve is moved to disengaged both sway bar ends by a fork activated by a plunger. The plunger is driven by a motor.

To disengage the motor releases the plunger and a return spring to pushes the fork, and sleeve, back into place when the splines align.

The motor can be worked around with some air or a screw, or rewired. There are kits for for air or screws. Rewiring seems a bit more work.

I suspect the splines in the middle are press fit on to the sway bar ends. It has to be two pieces otherwise they couldn't get the aluminum housing around it. It's unlikely to be welded to the splines because it would loose it heat treat and temper. So "I think" it might be removed with a bit of mild heat and a press.

The worst case is cut the Rubicon sway bar ends remove it from the housing. Then mill out the interior of the spline to slightly smaller than your sway bar. Heat the spline and press fit. Pinning it would help too.

The trick is to get a custom 2-piece sway bar that would fit the splines. Then heat and reattach the splines and install.

Yeah I know easier said than done, but someone somewhere must have at least thought about it.