Hey, I'm not against the Octolings for Multiplayer at all, if anything, I'm definitely for it! It would bring some fresh new experiences in Multiplayer.
Single Player is the story and how everything you see around you is the way it is, including Inkopolis. The Multiplayer in Splatoon is just you playing the sport for any reason you see fit. But the story around Inkopolis still applies even to Multiplayer, and it explains why some stages are the way they are, and the weapons you use are the way they are. The Bamboozler MKII is not the one used by Cuttlefish in the Great Turf War for example but a modernized version of it. Overall, the game is not going to break the canon it established just because "it's multiplayer!" so It will be interesting to see why the Octolings play Turf Wars with the Inklings in the possible near future.
For right now, the game explained why we can't play as Octolings. The characters we play as, the Inklings are not on friendly terms with the Octolings. In fact, all of them are underground. So I'm just curious as to what's Nintendo's likely funny reason on why they're friends again. Through a new campaign or other means.
That's all, it was curiosity, not me saying "They can't work as playable characters and here's why!" At this point I fully expect the announcement by the end of next week. I liked the lore that was built in Single Player. And I am looking forward to their explanation on the treaty between the two races. Because if there's going to be a sequel, Octavio may have to get a new evolved race to do his dirty work in the place of the Inkling's former enemies. As I see Octavio as the "Bowser" of Splatoon.