I've changed my mind... after reviewing the appropriate paragraphs, I'm going to comment on legality after all. And this isn't about the washer bottle (although I agree with Andy... that bottle must remain unmodified, IMO).
Rather, this is about what I see as a conflict between GCR 9.3.37, which applies to all competition cars regardless of class, and the ITCS. The former says every race car shall have an oil catch tank for any engine crankcase breather, period. The latter says your IT car is permitted a catch tank, if an engine breather line is disconnected.
So which is it for an IT car? Does the "...shall be equipped" wording of GCR 9.3.37 apply, therefore making a catch tank mandantory? Or is it that a catch tank is "permitted" and therefore optional, but only if another condition is met? Seems to me that a major part of ITCS 9.1.3.D.1.i is superfluous at best, conflicting at worst. Incidentally, the SSCS makes absolutely no mention of catch tanks... do the showroom stockers run them, or not?