Hi,
I do not see how a QLingo extension will help, as QLingo can't know the count of pages per recipient, it is pre-document composition. hence sadly it sounds like a dead-end to me.
I'm not sure it will help, but you can have an ADOR with the number of records using the QLingo 'GetEnv("CurRecordNumber")', this value can be accessed as (state.adorValue) and be used to generate a QR code that encapsulates both the recipient index and the page index\count, this is not exactly what you wanted, but is a piece of information that might help you achieve what you want at the end of the line.
if that does not help, I presume you'll need to raise a feature request.