[spoilers] Arrow was supposed to end with Oliver and Laurel moving in together, but CW forced the show to have Felicity and Oliver move in together after season 3 (which explains everything wrong with the past two seasons)

TLDR: There is very good reason to think the "Felicity and Oliver drive off into the sunset" ending of season 3 was supposed to be Oliver and Laurel in season 5, and CW forced them to move it up. And it explains virtually everything that has gone wrong the past two seasons.

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This is all speculation, but it has a pretty damn good foundation. Also, although I speculate that it was CW that forced the move, some good feedback in the comments leads me to think it could have been Guggenheim and the writers who forced the move despite it making no sense to the story. What I am certain of is that the ending of season 5 was moved to season 3, completely running the show off the rails.

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Why Oliver and Laurel were going to move in together

Right after the season 4 finale I sketched out what I believe the 5-season plot was initially meant to be, based on what all we know from the first two seasons and how the show works. TL;DR is that the show is set up like a mobius strip, where in each season the flashbacks and present day would explore two sides of the same story, and over 5 seasons each side would loop back around to join the other.

(You can read the whole thing I sketched out here, if you have a while, its very long).

I turned on Arrow on netflix today near the end of season 1, and it turns out that the reason Oliver took Sara on the boat with him was because Laurel asked to move in together and he said yes but panicked and got cold feet. That means the real start of Oliver's personal journey came because he was running away from a life with Laurel.

The plot I sketched out literally has the 5th season ending with Oliver asking Laurel to move in together. It seemed to be a reasonable end of the mobius strip plotline, and I wrote it that way even before I saw in the show that its where the story started!

With the very start of season 1 during the present day being the center of the story, it makes for a perfect loop:

1. Start - Oliver runs away from moving forward in his relationship with Laurel

2. Middle - Oliver wants to be with Laurel but believes he can't

3. End - Oliver chooses to move forward in his relationship with Laurel

With how so many elements of the show were designed to parallel one another and create arcs that end where they began, I have very little doubt that the show was initially conceived to end with Oliver and Laurel moving forward in their relationship.

Why to think it was then switched to Oliver and Felicity

The mobius strip starts with Oliver leaving Starling, then coming back midway. To bring it back to the start, Oliver and Laurel would have moved in together while leaving Starling. After that, the full initial story would be complete, and when he came back in season 6 he could be happy-go-lucky Green Arrow.

This is exactly what happened with Felicity and Oliver at the end of season 3.

Most people will agree that the first part of season 3 was still strong; although there were some issues, it still felt like Arrow. Its the second half where things started to go wrong.

I'm now certain that CW saw the ratings Flash was getting with a more fun/happy style, and mid-season ordered Guggenheim to end the five-season Arrow plotline early, and start season 4 with a fun/happy Green Arrow.

edit Alternately, Guggenheim loved Felicity so much that he decided to hell with the existing story and rewrote the ending to force the Felicity/Oliver pairing to be the 'happy ending' he wanted. end edit

The fact that he came back in season 4 as Green Arrow always confused the hell out of me. The producers at the start of the series said that the 5-season storyline was about how Oliver Queen became the Green Arrow. The narrative would make the most sense if the story concluded with Oliver becoming the Green Arrow, as that would be the end of his present day journey, just as Oliver becoming the Arrow would be the end of his flashback journey. Having him become Green Arrow at the start of season 4 doesn't make sense--unless the ending for the fifth season was suddenly moved to the third season.

Why this would explain all the problems of the past two seasons

Felicity and Oliver being a forced end to a cut-short 5-season story explains everything that went wrong in the show.

It explains why the Oliver/Felicity relationship (that didn't work very well) was shoved down our throats toward the end of season 3. Oliver/Felicity worked fine as a temporary arc where she and Oliver wouldn't work out and she'd start something with Ray. But suddenly the writers needed Oliver to end up happy and heading off into the sunset with a girl. They didn't have anywhere near enough time to complete the Black Canary transformation and get a relationship with Laurel working again, so it had to be Felicity.

It explains the complete and total lack of a coherent plot this season: all the planning that had been done for 5 seasons was thrown out the window at the end of season 3, and they were left with a mess of half-completed stories and character arcs all related to a story they couldn't tell anymore.

It explains why the flashbacks are so useless: they literally existed in the first place to be part of the initial 5-season story. They threw out the 'present day' version of the story, but they couldn't throw away the flashbacks. Now the flashbacks exist for no purpose at all.

It explains why they killed Black Canary. They didn't know what to do with her, and for good reason: they'd spent 3 seasons tearing her down and starting to build her up again, so that her arc could peak in season 5 where she and Oliver finally reach the end of their journeys, together. Whoops. Oliver was suddenly no longer on his journey, and Laurel's journey had nowhere to go.

And it explains why they keep doubling down on Felicity: they have nothing else. Between the CW's constant meddling and the complete annihilation of all the hard work of the first couple seasons, there was very little way to rebuild the show with a new legitimately complex multi-season arc, nowhere to really go with the characters, so they have to downsize the budget and reduce the scope of the show. With no budget for realistic action and no character development for realistic drama, what else to do but focus on the fans who don't give a crap about any of that, so long as they get their romance?