Open up expireType through a hook?

I’m using this plugin in a client project, and I’d very much like to be able to add my own ‘expire types’. My client wants the plugin to not update the post, but send a warning email to the admin so he/she can take manual action. I know this is not what the plugin was designed to do, but I think a hook for this would open up lots of other possibilities.

If I had a way to hook into the ‘how to expire’ select box and add “email”, I could then hook into ‘postExpiratorExpire’ and send the email from there. Since expireType ’email’ is not handled by the ‘postExpiratorExpire’ function in the plugin, this would achieve my goal.

http://ww.wp.xz.cn/plugins/post-expirator/