.... You're kidding right?

It's not about Ease, it's about gameplay and convenience.

Can you imagine playing any other type of game that requires shooting. Placing down the controller, and reaching for an entirely separate button somewhere else, just to shoot a target? In a fast paced game, any sort, You'd miss 100% of the time.

If you want more difficulty, that's why there are difficulty options, such as Impossible mode. More bullets, a faster moving target. Possibly extra abilities not seen in lower difficulties. You don't want a game that's difficult to control and play.

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~

Yeah, this won't happen. The controls are supposed to be like how Windows works.