The gun bobbing around makes no difference in any FPS games.
FPS games on the Wii is controlled through a bounding box method:

The outer rectangle represents your wide-screen TV(I was drawing a diagram using acsii but it didn't work out, so now it's a real pic). The inner rectangle represents the
invisible bounding box. The dot in the center of the bounding box, is your pointer/cursor.
How this works: Neutrally, and naturally, you should be aiming on the center of the screen. In your example, when the enemy runs left, you move the pointer slighter outside the box, then the screen starts turning. The farther you push the pointer, the faster the screen turns. In your example again, the enemy stops to shoot, you slowly readjust your pointer so it comes back to the center.
Ok, I understand where you're getting at. You want to be able to point at the top corner of the screen, and shoot there immediately without turning the screen. Am I correct?
This is
why MOH2 will boast the best control scheme, allowing you to adjust the bounding box to
your liking. Decrease the box for more sensitivity, if you make it TINY, it will play exactly like a
mouse. But in
your setup, I'm thinking you want Red Steel type control which is:-

However, most users who wants to get the best out of Wii FPSes would opt. for the "advance" scheme like the first pic. Which is Metroid Prime 3's advance control scheme. It provides smooth turning, cursor doesn't get lost easy as such like in picture 2(ala Red Steel mode).