Hi Yoghurt, long time..it's strange how without even reading each other's threads we have similar ideas.I've just seen this thread of yours and I posted an answer of mine yesterday on an idea for a TVD series final conclusion story and this is what I said
'My thinking is pretty leftfield at this point but I am going by the fact that the show follows the books but takes liberty to tweak things.
1.Observation that I notice is the start of the show begins with Stefan narrating his diary entries..so we know he will be alive at the end of the show.
2.One of the brothers in the book turns human..so here is my story ending which would be perfect imo
Apparently in the books Elena becomes an angel, this may not turn out to be identical in the series and with the hunt for the cure foreshadowing events .I want the last season to be as follows. Just for simplicity's sake lets say that the final season is number 6.So we find to bring back the main enemy of season 5 the travellers use the blood of Elena and Stefan,unknown to them it is some demon entity that they have been duped by to come on this plane.The witches to battle whatever dark foce comes through traveller magic try to kill Elena and Stefan as the link to this entity so that it dies. Damon in an attempt to save Stefan(or Elena) offers to sever the link between them by drinking blood of either of them to the point of death so that only one but not both die..Stefan offers himself to save Elena and Damon drinks from him and he 'dies' as a vampire. However before Stefan dies in the 3rd last episode, the entity possesses Elena so that it is secure no matter what knowing that no one would harm his new vessel Elena.In 2nd last or last episode Stefan is resurrected by the angels who are ancient enemies of this entity and tell him he can save Elena. So Stefan using his new powers destroys this entity in Elena and somehow cures her in the process.
So in the end Damon remains vampire(perhaps Augustine), Elena turns human and Stefan becomes an angel. I think this would be the best ending.'
So basically I feel the Marcos/demon from the otherside will play a huge role if they want to introduce the other species i.e angels .Anyway but I would love for this story to pan out just as how I've made it up.I really want it to end in a similar way to the books but instead of Damon(in the book) ,Elena becomes human(in the series) and instead of Elena(in the book) becoming an angel, Stefan becomes an angel(in the series)