Thanks for the list. My understanding is that RPi 1 Model A or B (which has 2×13 pins) has long been discontinued, I am not sure where to buy them actually. All other RPis use 2×20 pin header, and should fit in the current enclosure. This includes RPi 1 model A+, which also uses 2×20 pin header.
Also we have started shipping OSPi version 1.5 since a few weeks ago. Version 1.5 uses an improved switching regulator and can provide up to 2amp current on +5V line so should be able to drive all RPis without needing external USB power supply.
Though, technically, to really deliver 2amp it would draw quite a lot of current from the input 24VAC adapter as well. For example, to deliver 2amp @ 5V and assuming 70% efficiency of switching regulator, it will need to draw about 600mA from the input 24VAC, which is a significant amount.