BL is the country code for a small island: Saint Barthélemy
http://en.wikipedia.org/wiki/ISO_3166-2:BL
http://en.wikipedia.org/wiki/Saint_Barth%C3%A9lemy
The way the ISO currency codes work, the first two letters are an ISO country code, and the last letter is determined by the country itself.
We have a good precedent in ccTLD's (domain names), where small island nations which were blessed with a useful country code have leveraged their names. I don't think selling ISO currency codes will be nearly as lucrative, but the same principles apply.
Finding the right person or group to speak to would be the first challenge, then the ISO. The island is not presently marketing .bl domain names.
neat idea, but i think your over thinking this. crypto's have no boarders... lets not limit ourselves.
Could be an interesting little side project/publicity stunt though.
+1million. There are no limits.