You're thinking of Dr. Watson. He was only the 'Stranger' for Myst V.

I think the plot would work well using the puzzles to carry it along.

Using the example of Myst 3: (and i know you aren't thinking along the lines of tv-ifying existing games, but just to explain my point) The first season would comprise the arrival of the stranger or whomever was going to be the cast of characters in J'Nanin. The premiere would of course involve solving the elevator puzzle and watching Saveedro escape with the precious Releeshan book. As episodes progressed, they would work through the book-protecting puzzles and by the end of the season would have realized that the combinations for accessing the linking books were found by using the little telescope viewers in the top of the central tower. Of course, there would be the "human element" to delve into as well, things like "What can we eat? Where will we sleep?" and "Who's in charge here?" and 'That's the stupidest idea I've ever heard of! Why would turning all these useless little lightposts around fix anything?'

Subsequent seasons would work through each of the other ages(i can just imagine the wild ride on the Amateria marble machine!! lol), with the final season (or last three or four episodes of that last season anyway) dealing with the final problem of being trapped with a madman in a very small and not entirely friendly place.

Admittedly, what i've described above is a bit of a combination of the "Big problem" (evil Saveedro) and "Mystery" (where the heek are we?) styles, but I think something like that would really work. If there's some kind of enemy (tangible or not) that is always a threat in the background, I think it would add motivation to the plot, even if most of the episodes deal with less dangerous things like solving puzzles and sorting out the social heirarchy of the characters involved.

Hope you can pitch your series idea, whatever it comes down to being, and be successful with it! I know i'll be watching

yeah the series is always about the characters, so i have quite a few new good guys and baddies... and some who you cant quite pin down

and there will be plenty of cameos for good measure... some of whom will be huge reveals when you figure out who they are

Perhaps we could use D'ni history as a basis for some of the main issues in the series? Not quite sure how it'd work, but it's probably worth taking into consideration.

Now, seeing as we've fleshed out the ideas, I think it's time we actually started making something more material.

... as soon as i get a reply from cyan, which may be never

Dangerzone, from your screenwriting class you probably already know that you don't need Cyan's permission to write whatever you want; only if you publish or otherwise turn that writing into a public medium do you need their legal approval.

You also probably know that such approval is almost never given without some sample scripts, several episode storylines, character breakdowns, a master-plan for the long-term story arc, and so on. (here's an example, for the ill-fated series "Carnivale")
This serves both as a starting point for discussion and gives the other parties - franchise owners, producers, investors -confidence that you can deliver good writing and good ideas .