I doubt you could possibly make a nearly 900 lb Harley handle like a sport bike, no matter how large the pocket book. It would be easier and cheaper to just have a custom bike made. However, even late model Harley touring bikes with the latest and "greatest" upgraded suspension from the factory will ride and handle better with a top quality fork and shock upgrade. Look around this site and you'll find suggestions for improvements ranging from fairly reasonable to wildly expensive. As long as you have reasonable expectations, I'm sure you will find something that will improve the bike. But if you expect it to handle like a real sport bike when you're done spending your cash, don't waste the time or money.
JMHO - Jerry