Ah, great to see there is some interest.

First off, I'll try to explain the idea I had a bit better.


I wanted to start with a model with a skin containing an alpha channel. The alpha channel determine how 'reflective' each part of the model would be(Just as you would do with normal environment cube reflection mapping).
Then you'd have the cube map, which would also have to contain an alpha channel. This alpha channel would determine the intensity of the reflection. For example the brighter the light in the cube map, the more opaq(or white) that part of the alpha channel would be.
So the alpha channel in the models texture would determine how much CAN be reflected and the alpha channel in the cube map would determine WHAT and HOW MUCH would be reflected.

This is all just me thinking as low tech as possible.

But while I was surfing a couple of other forums I came across a thread discussing whether or not KillZone 2 could really be rendered by the PS3. One of the people trying to prove it could, came with this link:

http://www.ati.com/developer/shaderx/ShaderX_DiffuseCubeMapping.pdf

For what I can gather this would be even easier and even better than my technique. There's a link to a demo which uses this method and it looks pretty good. Furthermore they say that there's virtually no performance impact.