This might be a bit esoteric but I have found that you can "upgrade" the ATV with storage by nailing a crate to it with planks.
However upon a game save and load, it becomes detached. If you drive the ATV, it will pull away and leave the crate and planks hovering in the air.
I dunno, maybe fixing this on a game load is out-of-scope for the game. Personally I'd love it... it feels fair, a reward for clever use of in-game tools, and also isn't overpowered (it can become detached easily on a crash). But in particular, if it can't be fixed, it might be better to prevent it from working in the first place. Someone might think this is a viable strategy, and later get caught with their pants down loading their game far away from home, and struggle to bring their stuff home.