Very likely not. We're limited by what phpBB supports, and no offense, but there is absolutely no way I'm going to write a custom patch for phpBB for something so trivial.
![smile :)](./images/smilies/smile.gif)
Edit: To add to this, it's not a MySQL problem. MySQL supports 4 byte characters in the version that we are using, but phpBB does not. There's talk that they may support it in a future version, but it does not currently do so.