Don't call it a monad, call it a structured data type or something, that's what it is! Calling it a monad is like saying that you're using a curve of constant normal intersection point. Why not just say it's a wheel?

Yes, it's mathematically true that you're having a smooth ride precisely because the normals have a constant intersection point, but it's also true to say that it's a wheel and it goes round and isn't bumpy and doesn't scrape, and people can get a handle on that.

So yeah, use a Result or Option or Maybe structured data type because it keeps explicit track of whether there's a value or not, and yeah, you can change or combine them and preserve the tracking, but there's no point calling it a monad unless you're trying to make people believe that avoiding the $1bn mistake of allowing/using null requires category theory. It doesn't, it's just a structured data type. It's simpler than an array! Stop calling it a monad.