I understand, but think of any other game while holding a controller. Usually the right stick is used to aim, While another button is the trigger.
Think of the keyboard in the same way. Each button should be within reaching distance for the most control over any situation. Yeah, It would make the game easier for sure, But there's a difference between a Hard game, and a game that's hard to play. It's all about striking a balance between Easy to learn, but difficult to Master. :)
At least give my suggestion a trial, see what the response is from the public~ ^^ Hope it goes well~