I'm probably misremembering things since I forget the source on this, but I'm sure I've heard a story that Vince saw Kokina and loved his size but was going to pass on him because he thought two Samoans was enough, and that it was Bobby Heenan who suggested he looked Japanese and should be cast as a sumo instead.
Like I say, I can't recall the source on this, if it was Heenan's book or a shoot interview somewhere but I couldn't find anything on Google, unless anyone knows any better?
My memory is hazy as well, and I certainly can't recall the source, but I remember hearing that Vince was chomping at the bit to do something with the "big Samoan kid" but wanted something more high-profile than a tag team - he just wasn't sure what. Then someone (Heenan?) suggested the Yokozuna gimmick, and the rest is history.
BTW, I'm impressed any of you knew who Akebono was back then - the first I heard of him was when showed up at WrestleMania a few years ago.
I believe on one of the Legends of Wrestling Roundtables from WWE 24/7, Sgt. Slaughter said he was the one who pitched the gimmick of a sumo wrestler for Yoko.