Board Thread:Arrow discussions/@comment-9346948-20171128022612/@comment-24152851-20171201013710

A merge probably isn't possible, but they could have a Fake Crossover. Basically characters from one show appear on another, but it won't really effect the continuity of the other show.

As for Ra's al-Ghul. The best way at resolving that is he's a different Ra's to Arrow's Ra's. In Arrow lore, Ra's is a title not a person. So there can be more than one. They don't even belong to the same organisation with Arrow calling it League of Assassins while Gotham calls it League of Shadows.