We would like to thank you

Это значит Мы хотели бы Вас поблагодарить.
think-thank-thank Вы так подумали, что ли?Ведь think-thought-thought

Примерно вот так,проверьте, подскажите.

Dear Misters Konietzko and DiMartino
We have been the fans of yours animated television serial “Avatar: The Last Airbender” for the last 5 years. We would like to thank you for the greatest cartoon, we have ever seen. We understand that it was very hard to make such a beautiful animated TV serial. We are also aware that you have a wide range of fans in America and Europe and all of them love this  cartoon 
The last episode of Avatar: The Legend of Aang   was shown on television (ищем дату и вписываем).As we know after that was signed (подписано) many petitions for the continuation of this serial cartoon. We are also interested in it, but it is not the main topic of our letter. However, we would like to say you that many fans think that the story Avatar: The Last airbender is not over. It has some reasons for it:
1. Zuko did not find Ursa (his mother), but enigmatically asks his father about her.
2. As you remember Aang was the last airbender and lots of fans  are not be able to understand what will be after four hundred years because when Aang will die nobody will teach a new Avatar of air magic(много will посоветуйте как лучше).
3. How and why Airo to get in the spirit world. Why he so changed himself (не совсем подходит) after that? (When Airo was fighting with the Earth country he was very wicked).
4. Fans are not able to( может лучше can not) understand what happened with Azula. Because she did not mentioned after her defeat.
5. Finally some of us think that the topic about the spirit world is not exposed
We understand that it is very hard to make a new season of the “Avatar: The last airbender”. Our group discussed this theme and came to a conclusion that it will be good if you could make something like epilogue. For instance: “Twenty years after” or something like that cause of future is not clear(посоветуйте что лучше чем clear?).
The main topic of our letter is asking you about the future(I mean continuation) of the  Avatar : The legend of Aang. We are aware for sure  that the Nickelodeon channel purchased copyrights of Avatar: The legend of Korra. And we would like to know a bit more about it.
We thank you again for this beautiful and excellent cartoon. Moreover we know many channel television companies in Russia which will support your continuation of Avatar: The legend of Aang.   
We are looking forward to your answer for this letter.
Sincerely (Faithfully) yours.
(пишем название нашей организации, то есть группы и наш знак)