It is possible they built a two foot locomotive to that exact design, but the problem is that with the locomotives you pictured, the firebox was between the frame members. If you were to go to two foot with the exact design, the firebox would be too narrow. When going to two foot gauge or 20" gauge as the existing locomotives in Arizona, the firebox was put behind the drivers so it could be wide enough. If you are contemplating building a two foot locomotive to that exact design, it could be possibly be fired with oil or gas, but no solid fuels. Porter built some construction locomotives to two foot gauge with the firebox over the rear drivers but it was resting on top of the frame and the overall locomotive was rather tall looking, not at all like the design you mentioned. I corresponded with an individual that I have lost contact with who had a boiler from one of these locomotives with the builder's plate intact. I believe he was going to build a locomotive with parts scrounged from a wreck site of an identical locomotive. I wonder how far he got.
Bernie