[wp-xmlrpc] Enable XMLRPC without turn on in the admin

[Ryan Chan]

I want to turn on XMLRPC for users' blog without the need to change
the setting in their wordpress's admin.

Is it possible to say, create a new file xmlrpc2.php and copy this
file to under the user's blog and apply some hack in this file to by
pass the admin setting?

If yes, which file I should look at?

Thanks.