If you start a sentence with "as would...", as in "As would Napoleon, if he were here..." that implies that something has gone before, which is being commented on here. Without a previous reference, "As would..." wouldn't make much sense.
A clause can sometimes follow a comma, although a comma can be used in a long sentence to show the reader where he might take a breath, without losing track of the long sentence's meaning. (As in my example, here!)
As would a blind person never attempt to climb Mount Everest, so an armless person would never attempt to swim the English Channel...Or is that too fabricated and cumbersome?