Thinking "aloud" here, but you might be able to get something like this with the macvlan network driver with docker. On FreeBSD I'm able to use a bridge interface that has a VLAN interface as a member (e.g. bridge10 with vlan10), and then have my jails create a vnet interface within that bridge. To the rest of the network it looks like yet another host (including showing up in Unifi).