I don't think you realize how painful making an online mode would be. If you do any kind of research you would find a lot of game dev recommending to NOT make online multiplayer if it's not need.
Truth is I don't like multiplayer in general, if I would have wanted to make a multiplayer game I would have chosen Roblox because I don't want to create it from scratch.
As for the "other local multiplayer idea", it would have still required some online fonctionnality to it, hope you understand.
