One of the really cool features that you can do within the WordPress wp-config.php file is add in the FTP info. Then whenever you are doing something like upgrading a plugin or Wordpress itself, you don't have to go grab that FTP info and put it in there.
I'd like to see an additional set of questions asked for in the script. First, would you like to do this (I can see some folks having security issues since you are putting the FTP password into plain text...but then so is your SQL password already). Then what is the info needed. Then you simply add the following into wp-config.php.
*Add FTP login credentials to avoid WordPress asking for FTP details every you upgrade or remove something
* If you want to use a SSL connection, you can set this to true