Good point about the heat. I’m not as worried about the z axis stability, but the heat is worth considering, since both the laser and the driver have fans on them.
One reason I was thinking about mounting the driver near the laser was to reduce the number of wires that need to be routed to the tool head. Now that I’m looking at the wiring, though, I can see that there are some advantages to keeping the driver by the LCD (or at least away from the z axis tower) and running a bunch of wires to the tool – the main one being that when I swap out the laser with another tool, particularly an extruder head, I’m going to need to run a bunch of wires up there anyway.
I printed my remixed version of ductsoup’s mount: http://www.thingiverse.com/thing:1245848, which has mounting points for the fan and line lasers, so I just need to put it all together and wire it up.