I think hese things are hard-coded into the the game. I'm pretty sure you can't mod them. Even the boat hasn't actually been implemented yet, so even if you did make a mod that added that, your account would be insta-banned for having something that's obviously not supposed to be there. It's the developers' fault for being way more focused on running sales campaigns and p2w events.
The "under maintenance" issue, on the other hand, is clearly a result of something wrong with the mod. I wouldn't be surprised if we have to wait for the next official game update for it to be fixed. That's how it usually works around here. Probably so that the mod version stays the same as the game version, I imagine. Hopefully it doesn't turn into another DomiNations....