I'd say no. Low G on a soprano doesn't really work, the string is too thick to ring out properly. It would need to be even thicker, and thus work worse, on a smaller scale.
Sure it CAN be done. However, such a small body will probably not have enough resonance for the lowest notes. There's always the Romero Creations XS, though, which has the size of a Sopranino, but full Soprano scale length, and it comes standard with low G.
A wound Low G does not need a different nut width (usually). You can buy a single Aquila Low G wound. Put it on your sopranino. Tune it up. Play it. If you dont like it, you are out a couple bucks and you throw the High G back on the uke and go back on your merry High G playing way If you love it, congrats, your sopranino is Low G!