In that case, there should be no problem with any redirection, would there?
For "randomized load balancing," the Apache Foundation has this to say (using a RewriteMap). If you look under "Randomized Plain Text," you'll see that the URL changes (as it must) but to separate www1, www2, ... wwwx.
I understand (with your explanation, thank you) but the type of redirection you described would be the kind asked about by noobie hackers, ergo, my comment. Just understand that browser creators will not allow deceptions and mod_rewrite cannot hide an absolute (external) redirection. I'm thankful that they do and applaud their foresight.