there always exceptions to every situation. I've no doubt some men who were the product of insta-mason days turn out to be outstanding members. something just tugs at the back of my mind and it feels wrong for the long-term health of the craft. cultivating members who chose expediency over time and effort seems like one of those "it seemed innocuous so many ears ago, but bit us in the end" kinda things. sure it bolsters membership by giving more men the opportunity, but then again, we all know masonry is a major time sink. do men who do not have the time to give as well as receive deserve the craft? I do feel all worthy men deserve the light of masonry, but is that mindset going to get us in trouble some day? who can say?
EDIT: I guess I feel like one day masons should be a rarity much like the "made on sight" mason kinda thing. only done in circumstances where members feel very strongly that Mr. X would really make a great mason, but circumstances pretty much prevent him being able to attend degrees in a reasonable time (like military deployment or, in a case in my lodge, a member got sent to UAE for work for a year). Rather than skipping the degrees w/ the on sight thing, a one day could be done with, like you said, proficiencies to follow afterward. and never done as a "class", but by the actual lodge. I think it then shows great dedication of that lodge to its future brother in need.