Yeah, I too think it would be heavy and not worth the effort for what you get out of it. Maybe if you wanted to use an S size motor, you'd need all those gears to pull the weight AND have good top speed.
Like most auto-shifting tranny's, first gear is on a OWB and second is on a centrifugal clutch. I would think simply adding more centr. clutches for each gear thereafter would do the trick.