I'm sure someone would be able to put these to use... From looking at the pictures provided it seems like these would be good enough to be carved to fit a laser diode nicely. The collimating would have to be done using another module (maybe home-made) because I highly doubt that an AixiZ module can fit inside these things. Perhaps a brass module (the smaller ones) but probably not the chrome ones.
You want to be careful with heatsinks, you really want the thinnest layer between the diode and the air, if it's too thick it won't shift the heat quick enough and have an opposite effect of what you are wanting.
Personally I would point you towards heatsinks for the case style TO5 and TO39 transistors.
Not sure how much you will have drill or open them out but definitely worth a look.
Would post a link but don't have authority.
Well those heatsinks would be great. I am currently waiting on an e-mil from them about the core diameter.
And yes you are right, bigger and thicker is not always better If you have seen then one I used on my red there is hardly any mass to it at all. But works amazingly well.
"Bigger and thicker" is better if you're looking to transfer the heat to a host body. You want as much contact area with the diode and the outer casing as possible.
If the heat-sink is standalone, then yes, more surface area for airflow is better.