If Irrelevant is going to be a specific rating, I'd prefer to keep it defined as something superior to Immeasurable speed. I wouldn't mind the possibility of nuking it if the suggestions keep coming back to either just being another level of Immeasurable and/or something that is simply unquantifiable and is getting mixed up with abilities not related to speed.
Basically, either one of two things should be done. Find a definition that accurately treats it as a speed rating qualitively superior to Immeasurable speed without mixing it up with things like Dimensional Travel, Omnipresence, Nonexistence Physiology, Acausality, Transduality, ect. And obviously, speed shouldn't be mixed up with other stats such as Attack Potency or range; it shouldn't be something people need to be 1-A or have Outerversal range to qualify for nor should have said tier and/or range rating automatically warrant such a speed rating. And the other option should just be to remove the Irrelevant speed rating and make Immeasurable the new highest legitimate speed rating.
I'm getting tired of repeating myself, but I'm no expert on the uber high tiered stuff like 1-A ratings, conceptual manipulation, NEP, ect. So I am otherwise going to have to remain mostly neutral, but given I mentioned the option to just remove the rating, it sounds like I'm more or less leaning towards DontTalkDT's suggestion if that's what he ultimately prefers.