As much as I hate to say this, because it should not have been done with Laurel, this is actually a fairly realistic storyline if you're right, and one Arrow has not really done yet. Because I'm sure it happens often in real life, that one person doesn't realize that they have feelings for another person until Person #2 is gone. Of course Oliver previously had feelings for Laurel (that he gave up on around S3), but he's realizing that he still had them. And now he has to deal with that without being able to act on them. It would really be a heartbreaking and effective story if it weren't for them stupidly killing off Laurel in the first place.