I didn't mind the idea of addressing the Twilight of the Greek Gods. BUT, I think it was far better suited for Hercules, especially since it was always planned to form the basis of Hercules' sixth season and then when Hercules was cut short, TPTB decided to do the same story on Xena. I don't think it worked as strongly on Xena since, with the exception of Ares and Aphrodite (the Greek gods of War and Love), Xena hadn't had too much to do with the Greek gods.
Hercules was the demi-god son of Zeus. If anyone was going to play a large role in the Twilight of the Greek Gods, then it should have been Hercules. And a one-off appearance in the season 5 episode "God Fearing Child" wasn't enough.
That typed, at the end of the day, the Twilight of the Gods was a self-fulfilling prophecy. If Zeus and Athena had just left Xena alone, then they wouldn't have died and they probably would still be around. It was only their own arrogance and fear of "mortality" which lead to their deaths. Well, that and their own stupidity since their inability to kill two women and a baby was hilarious!
I'm not sure what I would have done differently if TPTB insisted on keeping the Twilight of the Gods angle. I don't think it was necessary as there was enough juicy material in season 5 with Xena's pregnancy and Gabrielle fully embracing becoming a warrior. One of the writers (George Strayton) had an alternate proposal for season 5 which I quite liked.
I guess if I'd been in charge, I would have kept the general idea, but I would have revealed towards the end that the pregnancy and the prophecy of the Twilight was all manufactured by the God of Love who had manipulated Xena, Callisto, Gabrielle and the Greek gods. Xena would have figured it out and would have fought against the GOL with the assistance of selected Olympians in the final battle. The GOL would have been defeated, but the Olympians would have realised that their time as the reigning deities was perhaps limited and may have decided to become better "people" as a result.
I know it was done on Angel, but I probably would have had Ares kidnap Eve and take her to another dimension where time moves more quickly to train her as a warrior for the Olympians (believing that Xena had aligned with the GOL and would be his/her champion). They could still have the Xena vs. Eve conflict, but it would be resolved far more quickly and adult Eve wouldn't have to deal with a bunch of guilt become she killed thousands of innocents. Heck, Ares could have even turned over a new leaf of sorts of Eve may have gone off to become his "Warrior Queen" who tried to bring about peace (through warfare). That would have left it open for future conflicts between Xena and Eve (or for Eve to assume Xena's place as a champion for the greater good).
As for the pregnancy, I'm more than happy with Callisto being the father. To me, it made perfect sense. Xena stole Callisto's parents from her. Callisto stole Xena's child from her. With the birth of Eve, a spiritually cleansed Callisto got the parent she wanted and Xena got another chance at parenthood. I couldn't think of a better way to explain the pregnancy. And I was happy for it to be written into the show.
I wasn't happy about the fact that they had Gabrielle embrace her inner warrior (and killer) to "defend" Xena because she was supposedly weakened by being pregnant, yet pregnant Xena seemed to have more super-powers than regular Xena! They didn't need to make her helpless, but seeing a heavily pregnant Xena jumping, flipping and battling armies was incredibly implausible, even for that show. Heck, when Xena was pregnant with Solan, she was still involved in battles, but in a semi-realistic manner. And if Xena had been weakened, then Gabrielle stepping up to become her personal bodyguard would have made a lot more sense. As it was, Xena didn't seem to need ANY help.
I agree that the finale should have been set in Greece. But, Rob Tapert's love for Asian action/ghost story films prevailed. To be fair, his love for such ideas had previously resulted in The Debt, which was awesome!
And I also agree that Eve's personality really needed some work. I didn't mind her in Coming Home where she did use her abilities to at least help the Amazons in the opening battle. But, once she became a mindless preacher, then I was happy to see her written-off. The fact that she still went around preaching the way of the GOL after Archangel Michael arranged for her to be killed as a martyr to the cause was pretty embarrassing for the character.