You can use $gettok() to get part of a string, see /help $gettok, which has examples for pretty much exactly what you want. Use that in conjunction with the above $replace or $regsubex code to "scramble" it.
As for your response to point 2, note that my point was sorting ranks is only expensive if you run it at each user request (!rank). If you do it at the end of each round for all [active] players, it's actually not that expensive. If you continually prune the list to a "top 10" or "top 20", it's not that expensive at all.
