That is a trip eDJ! No wonder Dan has been bugging me ALL DAY to look at it! LOL
Why mess with the chain? drill a hole in the sprocket and use one of those brass cable stops. I belive your 1st drawing would be the strongest mechanical advantage (see disclaimer below).
The chain may add to mechanical advantage but IMHO too many moving parts. On that note, I would be drawn to the second drawing with one large pulley. My approach has always been build it and ask questions later.
Now I have to be on the lookout for a 26" coaster brake rim in the dump! LOL