You've pretty much summed them up there Macca.

Closed alignment can lead to pulls (with a square face to swingpath) or hook (with a closed face to swingpath).

Topping it will also happen because the closed nature of your stance will bottom your swing out before the clubhead reaches the ball.

It'll be a bizarre feeling to change to a square stance as you'll feel so open and probably think you'll pull the ball even more left! You will to start with, I reckon, but the adjustment won't take long.

Just try it and trust it. You'll probably find you can time your arms and body rotation better too. Closed stances can see an armsy swing and a stalling body. A recipe for lower back pain!

__________________
Luke: I don't believe it!
Yoda: That is why you fail.