Could the new fuel switch for RCS fuel also be implemented for stock parts, or is it solely SSTU?

Its a fairly generic PartModule. Should be usable on stock parts (the fuel-switching bit at least). You could even potentially add an 'LFO' or 'XenonElectric' fuel selection to the module with a bit of additional work.

However, I'm doubtful if I will be including any such patches in SSTU. I've deleted the stock RCS parts in the SSTU-OptionalPatches, and as the regular SSTU install doesn't touch stock parts, any such 'stock-RCS' patch wouldn't have a home anywhere in SSTU.

Just for personal use. I've patched stock parts to use hypergolics, and was just wondering if the fuel switch could be used on the stock parts as well.

Yep, should be able to add it to the stock parts without problem. Look at the ModularServiceModule config for examples of how to set it up without the 'structure/standoff' switching stuff (just for fuel switching).

(this is another module that will be seeing changes in the near future -- splitting the fuel switching off from the structure/standoff functionality)

With the scaling ability and now the awesome recoloring, I no longer have a need to use stock RCS :)))

I didn't notice the rescaling option until yesterday :)

Closing question -- fuel switching will be present on all (non-integrated) SSTU RCS parts.