So the following which I'm writing is just to discuss whether something like this is even possible or if any of you would have any better ideas/suggestions or understanding how this might work. I thank anyone who takes time to read this in advance and I hope I don't explain myself too incoherently:
Let's say I have a page in WordPress which has a little bit of text and a video. Basicly I would like to share that page's link or I'd want to forward that page via e-mail to a certain group of people (let's say 10-50 specifically chosen people) and I want to track who of them opened the link and for how long they were on the page or watched the video.
I would like to make this happen in a way that I wouldn't have to make 50 different pages or 50 different URLs for each person (or 50 different tracking strings for that matter). Or that I wouldn't have to take a newsletter-mailer type page in between this process. Basicly, I would like to make the sharing/forwarding and analytics overview process as easy as possible, so that an admin or moderator wouldn't have to check too many different pages to get the info.
I really appreciate any and all feedback.
[Also really sorry if I posted this in the wrong place. Please feel free to redirect me to a corresponding slot].
Technically, Google Analytics isn't meant to be used to track this specifically- it's typically meant to track groups of anonymized users. That being said, it is capable of doing this (but may not be as automated as you had hoped).
You are correct in thinking that you'd either need to duplicate the pages or create multiple different campaign URLs.
The other thing to keep in mind is that as emails are forwarded, there is no way to update the URL after the email has been sent, so if you email me and I forward it to someone else who clicks through, you're going to think someone else is me.
One way around this would be if you know your users IP addresses (not only is that a big "if", but it can also be spoofed), or some other uniquely identifying feature (any chance these people have signed-up through your website and have actual user IDs? That'd make things infinitely easier!).
Maybe you could customize the email to add their email address as a query string? That could still require a lot of work (and you couldn't just share a single link).
Now, you can not store personally identifiable info in GA (including IP and email addresses), but at the server-level you could assign a custom dimension with a uniquely generated ID and send that to GA. Now you've got all the info you need!
Unfortunately this method only works if you can detect some kind of "fingerprint" of your users.
Unfortunately what you described isn't quite what Google Analytics was designed to do. If you wanted to get into detailed user-specific tracking, I'd advise you look into a CRM. Those systems are designed specifically for user tracking as you described.
Hope that gets you pointed in the right direction.