Why does it need to be a 3D shooter?
Take the elements of MW3 that make it MW3 besides its perspective. That's how you properly port a game, you have to get to that layer of abstraction. It will not look at all like MW3 but it's probably better because it will be tailored to the Amiga's capabilities.
A good comparison? Compare the Metal Gear: Solid games to Metal Gear 2 on the MSX. Both are as deep and cool because the basis is the same.