I'm not sure I'm the right person to raise this question but I wondered what the current thinking is on adapting the code for other character sets. If I recall correctly we or now assuming UTF-8, right? What exactly does that mean, btw? That we changed the MySQL character tables for those above 7F? Anyting else?
The English Wikipedia, and the German one being tested now, are both ISO-8859-1, not UTF-8. UTF-8 will be needed for Polish and other languages. There won't be much software change involved; just telling MySQL to index the right way.
As for a special notation for accented characters, I'm not fond of the idea. Foreign users should have foreign keyboards. Others should still be able to enter accents by whatever means their OS and browser allow, and I'm not aware of any that don't have some feature for it. I don't like duplicating effort that should be already done elsewhere.