My reply to
@T-K-G from the show thread showing how I would have kept Oberyn alive:
Tyrion's storyline could be slightly changed to his being exonerated through Oberyn winning the trial by combat but knowing that Cersei will have him killed anyway, Jamie and Varys set it up for Tyrion to secretly get out of King's landing without Cersei finding out. The rest of Tyrion's story can play out exactly like in the books from Jaime confessing about Tyrion's first wife not being a whore and that Tywin forced Jamie to lie to Tyrion which leads to Tyrion turning on Jaime to him then finding Shae fukking Tywin and killing his father in a rage thus becoming a wanted man again.
Oberyn could have been shown to have sustained some injuries in the fight with the Mountain that precluded him from killing Tywin himself. Oberyn's character could then become a merged character with his brother from the books. Say Doran dies of some illness and Oberyn becomes the new ruler of Dorne which then makes him have to leave the Small Council and King's Landing in a hurry before he can kill Tywin himself...with season 5 featuring a bumped up presence of Dorne in the show then it becomes very easy to just have all of Prince Doran's storyline from the books be carried out by Oberyn with the excuse for Oberyn not going after the Lannister's himself being because he has accepted the responsibility of the ruler of Dorne and his temper needs to be controlled. So then Oberyn becomes the one plotting against the Lannisters and wanting to align with Dany so she can claim the Iron Throne.