User blog comment:DanteRedgrave/Build-An-Ending/@comment-1.54.154.208-20140429170601

Might be a little late, but still, here are my ideas:

1. Vanilla Ending: This is what we want, Issei has a wedding schedule with every girl in his harem, with Rias being like in his dream, Japanese style with Akeno, Koneko (actually a double event with Kuroka), Irina and Kunou, Italian style with Asia, Xenovia, Ravel. Rossweisse is traditional Norse style in Valhalla where Vali would crash Issei party, attempted to kidnap Rossweisse to build up Issei murder intent, God Thor later would knock them both, then challenged them to an ale war, Azazel shot Vali with the second Gender-Bend Gun, thus Vali heated up for Issei, ended in a comedic style when Issei wakes up think that was a dream but seeing female!Vali and Yuumi sleeping next to him.

2. Timeloop Ending: The fight with 666 is out of control, Great Red, Ophis together with everyone die, only Issei survives, after million to million of years swimming in what left of Dimensional Gap, Issei becomes a mass of power, from his essence, Gods, Dragons, all kind of life form and cosmologies of Earth born while Issei slowly turns into the "new" Dimensional Gap, his "Nothingness" becomes "Infinite", after thousand to thousand of years, the Dimensional Gap gives birth to Great Red, who previously was Issei. The timeloop continues until GR!Issei realizes what has happened and keeps everyone alive, seeing his otherself finally reaches the happy ending he always wants. GR!Issei dreams and meets his lovers in the previous timeline.

3. Open Ending: The fight with Qlippoth reaches the end, but Rizevim has successed, he finally escapes to another universe, thus, Issei with his harem (now strong enough to fight against god-class on their own), ride on the Ryuuteimaru spacecruiser into the new journey.

4. Timeskip Ending: M&M meet Issei in a small restaurant, they talk about what happened after they got their first job (of course in Issei's case it's a fake one), complain about how Issei was so lucky that Rias Gremory married to him, but at the same time Akeno and the beauties of Kuoh Academy still living in his house, never married, Issei replies that they are working in Rias company, and his house happens to have enough rooms for them to hire. Later Issei meets Saji who's escorting Sona to a baby-shop, showing that she's a soon-to-be mom. When Issei returns home, all the girl is waiting for him in bride dresses, they tell him that it's the universal day of their wedding.