Better late than never...
I managed to implement this feature. I couldn't find a way to do it, but with some guidance from Mr Jenkins himself recently, it's now done.
I will make a new release soon once I've fixed a few small issues, things are stable and perhaps when I have another feature ready.
I've been testing this feature and it seems to be fairly stable at preventing two jobs using the AVD at once.
In case you're interested in trying it now, I've attached a build with the feature enabled. Only one AVD of the same configuration should ever run on a given computer – other jobs which need the same AVD config will remain in the queue until the first job is finished.