Thought about it as I have access to some NOS Mavic 317 disc rims in various colours but they dont seem to have a braking surface...it might be worth a laugh to have a crack at trying to stop a pair with canti's!!
or any, one advantage of discs is a lighter rim through not needing a braking surface. Is it a particular rim you fancy? Some manufacturers make them in both disc specific and rim brake.
good ol CRC have sent me a Sunn Ringle rim for disc. Checked my order and the ad. No were does it state which type of brake. Get the very nice rim and a sticker states disc. :x