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Works fine on my phone.

I think Q and E is the best sollution in my opinion,or go with 1 and 2 if you really don't want those keys.

Best option would be to make the controls programable, most people now have over 5 buttons on their mouse so being able to reprogam it as they please would be the wisest thing.
If that's not possible how about this, clicking the mouse scroll brings up the gun menu and you chose which wep you swithing by clicking left mouse button for left hand wep and right button for the wep in the right hand and then scrolling to get to the desired wep

I suggest you let me die when I fall.

I would suggest replcing Q with Scroll Lock and E with Reset. It just seems logical.

shift + left/right click?