Ideally the more unique points of reference you have the better. I'm sure you could up the accuracy and useable range of the Wiimote if say you have a different frequency IR Emitter at each corner of you screen. Effectively giving it a bounded box.
A good way of thinking about this is to look at your TV. Now look at the Wiimote bar. Imagine that the room just went dark, you can actually see the light emitted from the sensor bar, and you where trying to define the shape of the TV from just those two points of light. Hard isn't it. Now lets say that instead of the 2 sensor bar lights that instead you have 4 points emitting light. One for each corner. It's now much easier to define the TV's shape and dimension. Imagine that the lights suddenly went dark again but you could only see 2 of those points of light and someone asks you what edge that those two points represent. It be hard to know with just that information. If say instead each of the light points had its own unique color, you could now for a fact that those points you see represent to top edge of the TV.
Thats how I think it could be improved.