I have almost that same bike, and I made some mods of my own recently:




I absolutely hated the grip shifter, so I replaced it with a Shimano Rapidfire shifter instead. Didn't want to go to a bullhorn bar so I added grips with integrated bar ends. Replaced the lousy stock crank with a two piece crank with external bottom bracket. And installed my Brooks B17 saddle.

I do like your idea of putting a wheel at the bottom of the seatpost and using a bungee cord to keep the bike tightly folded, though, and I'll definitely have to look into doing those myself.