For bug 1592811, we have the limitation that networking for LXD container is over lxdbr0 which is not attached to any physical network. What happens is that if we want to have a dense deployment, then the LXD containers come up on a LXD internal network which cannot be reached from a different host. This doesn't work since lxdbr0 is not tied to an external network; hence, all the Juju services cannot be deployed successfully.
Per conversation with frobware and mackgreagoir, perhaps juju can provide one or more additional config options for specifying a bridge to use instead of lxdbr0 and also the location of the cloud init image with the bridge already configured.
frobware asked me to follow up with a bug on this to describe the issue and request. So this would be a request for Juju config option for specifying the location of the cloud init image so Juju could point to custom cloud image's location. In that case, the image would have a bridge configured on top of a NIC. Then, the bridge name would then be a Juju config option or it could be a known bridge name such as br100 or br-int which would not necessitate a config option for it.
Adding cloud-images to follow up on whether it would be possible to re-provision the OVA with a bridge over default physical network.