I wonder if you're planning to implement dualSrcBlend to a Vulkan driver later at some point (currently not supported), perhaps we could raise it if it's yet not planned?
Our Vulkan renderer will use it if the Vulkan driver supports it
Cheers
For what it's worth the current hardware wouldn't support this natively anyway, so it's unlikely to give you any performance uplift and you could get the same effect by emulating the more complex blend equation in shader code.
HTH, Pete