The simple fact of the matter is that Netflix don't really care who you are or where you live or what content they provide you. Netflix wants your subs

Netflix wants happy licence-holders to keep getting the content to encourage more subs.

IP holders divide up licences by region in order to sell them for the highest price so they have an interest in Netflix enforcing region based restrictions.

Netflix know they will lose many users and therefore subs if they are effective at stopping VPNs/proxies.

So Netflix will improve and expand their attempts to stop people bypassing the content restrictions to keep the IP owners happy but they will be careful to keep just a step shy of achieving this goal lest they lose their subs.

But then again, who does?

My brief experience with this was really rather annoying. the filters activated a couple of weeks ago. A bunch of websites (inc my porn) just gave 500 errors. I was not taken to a page to explain what was happening. I only realised that my Cameronwall had been activated when my friends confirmed that they could still access the sites I could not. I logged into my BT account, found the part where I turn them back off again and did so only to be told that it would take up to 24 hours for the change to take effect. Additionally my partner's Macbook started to give a range of weird errors when connecting to a variety of webpages. I'm not overly techy but it seemed our router was remembering the redirect and still using it for a bunch of sites (even though the block had been removed by this point) and the macbook was refusing to display the sites it was being redirected to because it had detected a suspicious re-direct.

Maybe QR code repeated around the edge of the invitation? then to a lay person it'd look like decoration.

make the invite an ARG? you do run the risk of not having any guests show up though.