I think having the punycode form have no "value" on a name badge. Punycode, as it is designed, is meant for machine-to-machine communication.
So why don't we come up with a machine-to-human transliteration mechanism? So if someone called ÎÎáÏ (trouble with spamcontrol again...) a translation table could turn this into Zeus and back again where appropriate. If the translation table doesn't know "ÎÎáÏ" this could be translated into ZITA-epsilon-ypsilon+grave-sigma, which isn't great but still much better than just numbers or base64 or whatever.
But I like the idea of allowing participation to put their own native names together with their ASCII version on the name badge especially for the next IETF.
But...
1. What if the person don't have ASCII only name? (e.g. Patrik FÃltstrÃm)
I guess do the same thing as is being done today...
2. What if the person have a name which the computer cant be printed?
(Maybe it is not in ISO 10646, maybe it is but there is no fonts,
maybe the fonts is there but the rendering is wrong?)
Easy enough: allow people to supply a graphic.