How can a metacontact always send to one contact by default?

[Boris Gjenero]

For one metacontact I would always like to send to one contact under 
that by default, even if that contact is offline and others are online. 
I know that after opening a chat window I can use the "Send To" menu to 
change this, but this doesn't persist and I keep forgetting to do it.

We generally use Facebook (via https://github.com/dequis/purple-facebook 
or a browser). His Facebook contact changes between online and offline, 
while the Skype contact (via 
https://github.com/EionRobb/skype4pidgin/tree/master/skypeweb ) goes 
idle instead of offline. So, when the Facebook contact is offline but 
the Skype contact is idle, double clicking on the metacontact defaults 
to sending to Skype. But, I want to send to Facebook, because I know the 
message will be delivered and I want to keep the conversation there for 
convenience.