I had Lucene installed and I upgraded to Elastica for a Ancient Greek dictionary. However, although Lucene by default would provide diacritics-insensitive autocomplete and search results, it appears that for Elastica 1.7 one needs to use the ICU plugin. But no such option appears in CirrusSearch for MW1.23 (nor in CirrusSearch.php For MW1.26, I could only see it here as $wgCirrusSearchUseIcuFolding). Is there any way to provide diacritics-insensitive autocomplete for MW1.23?
I'm not familiar with CirrusSearch etc.
But I hope this  helps you.