Honestly I do not see any benefit to replicating the current closed-loop fuel control during low throttle on the stock ECU. Everything is functioning as intended - if the stock ECU could run closed-loop fuel control during high throttle that would be something to talk about. Even if the low throttle closed loop logic could be extended via a hack I don't think the space exists on the stock ECU.
There are aftermarket stand-alones that will run continuous closed-loop fuel control at all throttle positions and this unit already has the output that those would use. If a piggy back ever comes out with this ability it too would likely use a linear 5v signal rather than an amp based AFR signal.
Just my .02