To answer your narrow question, what you need to be able to say is, where is the data that you are passing to the printer coming from?
A null profile in the sense of not changing the data sent to the printer is actually the same profile as whatever was generating the data used as its color space for that data. So there is actually no single null profile in the sense that you are using the term. Possibilities for internal profiles include any of the standard gamuts (e.g., sRGB, aRGB, ProPhoto, etc, etc) or perhaps the gamut of your display. By way of example, if you were using LR, and you wanted the same data as is shown on the RGB read outs to be sent to the printer, you would need a "Melissa RGB" profile for raw files, or the imbedded profile for JPEGs and Tifs.
But I'm not at all sure that I understand what it is that that you are trying to achieve here.