The communication between Amazon Echo and Home Assistant still isn’t straight forward. You have to connect via the cloud. I guess this is similar for other voice assistants. On the other end, the current devices don’t implement the matter protocol. A protocol translating device would prepare them for the future.
Matter is designed for vendor independent communication. Please provide a matter API to Home Assistant, so that Home Assistant can act as a general proxy for devices connected by other protocols.
Virtual devices should also be exported by the matter protocol, that observes like Echo can directly react to changes in this virtual devices. The virtual devices can be orchestrated by HA automations and external observes can react to them.
I don’t know the specification of matter, to estimate it’s limitations, though. A hardware controller is maybe required to send this API, if matter doesn’t simply work over wi-fi, too.
Hope the idea gets clear enough.