i once got a guy come down to the shop and ask me to drill his add wheel set so i took a few mil's off his rim walls, made holes in between the nipples and sliced some of the inner walls (where the tubes are held) i thought it was stupid but it was interesting... it shaved alot of weight and he still come by the shop stoked on his custom wheel that he still didnt brake (this was like 5 months ago)
Singlespeed hub, install a few cogs from a cassette, adjust the limits on your derailleur to limits its max and mins.
The rims, simply use a drill press prior to building up the rim.
(this was like 5 months ago)