Adam, that system appears to be used on a local network and not a WAN. Is your remote person within the same network as your vmix setup? If they are on the same network, how close to you are they? Have you considered using skype? There are several users here that use skype video in their vMix productions and using Skype audio work as well.

If my commentator was close enough I would be inclined to use a Sennheiser Wireless mic option. My commentators are beside me but I mic up the public game announcer with the Sennheiser mic and that works great for us. I would think that if your commentators can see the game/event you are streaming it would seem that he/she/they will be close enough to use the wireless mic system. However, I can see where an event like auto/motorcycle racing, golf, etc, may not accommodate a wireless setup. If you go with your original post option, let us know how it works.

Tim