I'm still buggin' so forgive trying to go further with this.
Wouldn't adding that extra pully sprocket in the rear, expanding chain length, making it wider in the back, slow down rotation? The above picture is an early derailleur invention meant to change speeds... the more chain the slower the wheel turns, no? More distance the chain point A (drive shaft) has to return to point A, no? If not why?
Oh, and good mornin' to y'all