So in other words, you'd remove Sara from the equation? That'd mean you'd have to rewrite the plot of the last three eps. And then you'd have to bring back Sara for LOT anyway.
See how difficult it is to actually break a story when you have specific beats to hit?
Why would I remove Sara? When I said "hilarity ensues", I was to lazy to write out the whole plot. But once Oliver makes contact with Constantine, I don't see how it would be hard to get him involved in the Sara plotline.
And that would make sense if they had more than one episode to tell the story. But they didn't. It's a lot easier to establish trust between Oliver and Constantine if they get some quality alone time. Which the island does nicely. Also the island storyline is about mystical stuff this year and it fits Constantine's storyline for his show so I don't see why it's that absurd. Oh, and they still need to make an episode of Arrow to boot, it can't just be an episode entirely devoted to Constantine.
PS. You pretty much described Barry Allen's introduction from season two. A two parter, no less.
In no way showed the 5 minutes on the island quality time between Oliver and Constantine and established some kind of friendship by the end of the flashback. It was rushed, no matter how you slice it. And yes, a two-parter would've been awesome, because more Constantine is awesome. And yes, I'd sacrifice an episode of Arrow in exchange for an episode of Constantine in disguise, if it has good writers from Arrow attached to it. This season is long and filler is bound to happen. Might as well make it around Constantine.
So he ignored Darhk for 30 years, but he is interested in him now because he is in Star City? Or Darhk just started using the magic he has for over 100 years just now? And he is attracted by the magic, but he leaves anyway because he isn't interested anymore when it turns out it is an immortal wizard doing stuff?
I didn't say he was interested in Darhk. I meant that he had some sort of dark magic case in Star City, like he had them all the time in his cancelled show, but perhaps linked to Darhk (without him knowing). Him leaving at the end made sense in both cases, because Constantine is an asshole, but less so, if him and Oliver as such good island buddies.
e: Please don't misunderstand me. I no way did I hate this episode or anything like that. I'm just tired of the island and the flashbacks in general since last season.