Ah, I see, I thought it was just an index.
So, apart from creating extra character styles (e.g. italics-pagenum, bold-pagenum) and applying these to the page numbers throughout the book appropriately, and then running LiveIndex multiple time for each such character style, I’m out of ideas.
The best solution, of course, would be an option in LiveIndex itself, say an option to find page numbers “Based on the current setup in the GREP find.”
I’ll add that to the feature request list but can’t guarantee when it will be ready.
If you would like a quote to add this feature urgently, send me an email.