How to Rename wp-login.php for Multisite?

First things First …

The Rewrite Rule
Basically all this rewrite says is (say it out loud) … when I type mysite.com/login and hit enter, then take the user (rewrite) to mysite.com/wp-login.php

This is not a URL mask or URL Forwarding which is what you are hoping for.

Second Part …

After Login – Redirect too
The url your are seeing contains 2 parts

  1. http://mysite.com/subsite1/wp-login.php
    • this is the actual URL for the login page
    • as @Brasifilo says you are better of telling your customers to go to mysite.com/wp-admin
  2. ?privacy=1&redirect_to=%2Fsubsite1%2Flogin
    • ignore the ?privacy=1
    • then &redirect_to=%2Fsubsite1%2Flogin is fairly obvious as where to GO after logging in successfully.

Hiding that you’re using WordPress
It’s probably better that your customers know that you have white labelled WordPress … it would give more confidence that their CMS is a trusted open source application used by tens of millions of people around the world. Don’t hide it 🙂