I'm looking at the more recent trends, not going back 3 decades, hence my pondering about whether going forward we are more likely than not to see dual threat QBs winning the award than drop backs. The hypothesis is that they have more "highlight film" moves. I recall one play by Troy Smith, who I think meets my criteria, making a throw off balance while scrambling that was caught for a great play and a key game.
It was shown over and over and made Smith look fantastic, along with other plays where he was very elusive.
Matt Stafford would be the other type, almost a statue, great arm, more typical NFL QB with a pretty solid pro career, but not remotely in the Heisman discussion.
Number One pick as I recall.
Anyway, something to ponder if we have a competition between two dissimilar QBs in the future.