It's not the craziest prediction at all. I could well imagine Holmes winning. Solid, fundamental, classic "boxers" like Holmes tend to match up well against faster, flashier fighters.
That Liston guy could box a bit, though. Heard he had a pretty good jab. I think Holmes' style plays to Ali's strengths, personally. Ali had trouble with swarming, crowding fighters like Frazier & Norton. Holmes gives him the luxury of thinking and attacking at will, and that tends to work out well for the faster fighter.
I wouldn't pick Holmes per se but I can see scenarios where he wins - he's a style problem for Ali, definitely. In fact, I'd pick him to win two or three (at least) fights out of ten if they fought that many. MTF