But I'm also playing devils advocate here too because Maul is just like Fett and all of the other background characters. He is just a henchman who looks cool, and is actually better because we know so little about him. This is same reason why doing origin stories on existing characters are almost always a let down because it robs our character of mystery which is what makes them so interesting in the first place.
This.
As many others have said before:
1. Fett should have been Clint Eastwood. The man with no name.
2. Han Solo . . . maybe a backstory could work if it's handled just right. But it's a bad risk.