As an answer to your question: the main idear would be to warn people that a show was cancelled and the final episode ended on a cliffhanger...
Netflix is a prime example: they keep pumping out new TV shows, the makers of the show end their season on a cliffhanger (because they think that would decrease their odds of getting cancelled), yet netflix still cancels them... The end result is: all fans of the show are left hanging... They saw the final episode (ever) ending on a huge cliffhanger which never gets resolved.
For me, this behavior is a dealbreaker: i refuse to watch an older show if i know it doesn't have a proper ending (an open ending can also be a "proper" ending, i'm basically talking about the shows that end on a cliffhanger, but it was obvious the show wasn't meant to stop at that point)... Offcourse, shows that are still running are always a gamble.
I'm trying to make a public database people that love TV shows could visit before they start watching an older show... That way they can look up wether or not the show they are interested in has a proper ending before investing a lot of time into watching a show that abruptly stops and leaves them hanging high and dry.
Really useful solution to the problem... but I wonder how many people will be interested in knowing whether TV Shows they are interested in have proper ending. Ofcourse, I know what it feels like to leave people hanging with cliffhanger after investing lots of time (plus the emotional attachments) on shows they find really interesting. I'm not sure how many people will be interested in avioding such shows if they are hard to resist.
Anyway I guess there will quite a number of people who will be very much interested in this kind of service/detail. Maybe you could get people to be interested if there are not alot out there.
By the way, I noticed you are doing this because no one has been able to do it like you want. In the end you may end up attracting people who want or would want thesame service