It would be nice to have the ability to add more ip address to the lan in order to have HA serving more subnet so I could have Apple HomePod/AppleTV in differen subnets. Whit avahi I can stream from different subnet but the Apple device need to be on the HA subnet.
If you have different subnets on the same physical LAN (without VLAN segmentation), you’re basically wasting your time because you gain no security from such a thing.
If you have VLANs, then your requirement basically demands that your Home Assistant device to be multihomed (multiple connections, each with its own IP and subnet, to each VLAN you want it to serve).
We have VLANs at home but HA is not multihomed — it has a single IP. The only special thing we have is a reflector for mDNS across multiple VLANs (avahi-daemon). That seems to work fine for our streaming needs (primarily Spotify and Music Assistant).