I show you my new plugin : MOTD Timer This plugin allow you add Timer in your MOTD (In server list)
If you want to change field in 'Timer:', you can but it is not needed

But you can change the MOTD when the timer is active (If you have the same bug than me (If you have a line break in the MOTD when you reload the plugin), normally it sould work too.
You can use %timer% in the MOTD to show the timer
You can share this plugin if you want