Have you seen this thread ?
http://www.elektronauts.com/t/using-ot-for-backing-tracks/5244
If so can you be a little bit more specific about what is not working for you ?
With your set up ( the second pattern’s one shot being trigged on a separate track ), you shouldn’t have to perform any re-arming on pattern change. As far as I know you can’t program re-arming into the arranger but have to do it manually. …but as I say it looks like you’re already attempting to work round that limitation
So where are you getting stuck ?