UTF-9

Via Stefan -- UTF-9:

Transformation between [UTF-8] and UTF-9 is straightforward, with most of the complexity in the handling of [UTF-8]. It is hoped that future extensions to protocols such as SMTP will permit the use of UTF-9 in these protocols between nonet platforms without the use of [UTF-8] as an "on the wire" format.

Almost, but not quite as good as this one.