Get your need. More I dunno how you’d do this without some complexity I think is my larger point. Perhaps a container would work since we’re talking about RB5009, but even with only one interface to containers, means the container needs to be configured with your VLANs too.
Since there is no mDNS or SSDP proxy builtin either (which are actually a UBNT built-in feature), this proxy’ing discovery across VLAN has come up before. Mikrotik’s response is typically:
With his colleague @raimondsp adding:
(full quote: http://forum.mikrotik.com/t/mdns-repeater-feature/148334/43)
So easy to imagine a broadcast proxy may not be in the cards as a supported feature. But I’m pretty sure a container could fill in this need, at least on the RB5009 – which is a nice router & supports containers.