Highlighter should support all MultiTermQuery subclasses without casts
Regex support and beyond in JavaCC QueryParser
Highlighter has already a test for SpanRegexQuery and the build dependencies are already in the ANT file. Here is the patch for RegexQuery
Those issues (LUCENE-2039) are kind of related as they eventually add more support for RegexCapabilities in Lucene.
Commited in revision 836162