Iām hoping to work on this today or tomorrow. 
Question: Do you like how your current mapping configuration works, or would you like anything changed about it? i.e. if you could have it ANY WAY YOU WANT with your web server, how would it be? Just like it is now?
One thing to consider: do you pre-generate this config and then reload it when any of those half-million-lines change, as a stopgap for a static config? (In other words, are you using this huge static config in place of a dynamic config?) Would you rather this mapping be dynamic? If so, how would you like it to work?
But if all things are to stay the same, this will be very straightforward and I can have this done by the end of the week.