2 of those are likely to be intentional. Tails in the background could probably cause a lot of weird issues if he was the only one there, and as for Tails not entering the submarines, this is a good thing IMO because if you for whatever reason don't actually want to enter, you don't have to worry about CPU Tails bumbling into it, or your friend doing it by accident either. Sonic should control all transitions from screen to screen when it comes to this kind of partner system unless there is a specified 2P Co-Op mode. As for the other ones, iunno. Also you're gonna have to pardon me for being a little put off that there's a request for a Director's Cut for a game that's not even 6 months old yet. Wouldn't mind a bugfix patch or anything though, but honestly I think we'll get there via modding so we good.