By the way, just some food for thought... Since my dialogue engine comes with a Visual Novel prefab I have been toying with the idea of creating a Visual Novel game for my website. Thing is that the code never needs to change between one story and the other, all that has to change is the text file for the story so I would build the game once and then just add new stories over time. One of the things I wanted to do was to allow site visitors to create stories also. Since they don't need access to the binary to do so I would then just give them a web page they can access via the Dashboard and have them write the dialogue in there.
In order to get access to this page in the dashboard I would just assign them a custom role or capability on my website (most likely a capability). Using WordPress Money I could sell them Dialogue Editing capabilities right on the site and as soon as the payment clears, voila, go to the dashboard and now they have access to edit / create stories.
This may be another avenue for you to explore. Give ppl a custom role on your site and then in Unity simply tick the box to fetch back the roles during login and inspect that instead of the custom meta which you won't have to write any more. This basically moves the automation from the Unity registration function into a manual process done on the website somehow. Not sure what it is you want to sync but by using custom roles you can give authors and consumers different pages on the website without involving my kits at all. In addition you can still check the roles like before so there is that... but if a custom role is overkill for your needs then the method in the previous post should work just fine :)
At least now you have options :)