Addressable containers on OpenStack are not yet supported, so the workaround you're describing is a possible way to get close to what juju does on MAAS (juju-br0 is not even created on OpenStack).
We do plan to have the same level of support for addressable containers in OpenStack, as in MAAS and EC2 (currently only with the address-allocation feature flag set at bootstrap), but it's not considered a priority vs. AWS VPC support for example.
Addressable containers on OpenStack are not yet supported, so the workaround you're describing is a possible way to get close to what juju does on MAAS (juju-br0 is not even created on OpenStack).
We do plan to have the same level of support for addressable containers in OpenStack, as in MAAS and EC2 (currently only with the address-allocation feature flag set at bootstrap), but it's not considered a priority vs. AWS VPC support for example.