This makes sense only if (a) your transport medium will only transfer graphical Unicode code points, and (b) you are interested in minimizing <i>code point</i> count as opposed to byte count.<p>If (a) is not true, you are better off just using binary as you state.<p>If (b) is not true, you are better off using Base64 if the underlying encoding is ASCII-compatible (e.g. ASCII, ISO-8859, or UTF-8), or Base4096 if the underlying encoding is UTF-16.<p>In the case of tweets, both (a) and (b) <i>are</i> true, making this somewhat worthwhile.