changing lightmaps with javascript / saving multiple lightmaps to lightmap array

Part of the game I'm working on involves turning on and off the lighting system inside a space shuttle. In the whitebox version I just used lights and turn them all off and on with a script. About halfway through production of the actual game I can see that in the shuttle scene all the lights are hitting the processor way too hard.
Since there are only two lighting situations in this scene I would like to bake 2 lightmaps (one for lights on and one for lights off) and swap them out when the player hits a button. I've done a little experimenting with lightmapping and 2 questions have arisen:

1) how do you save multiple lightmaps to the lightmap array?

2) I could figure this out, but if anyone wants to throw down an example of a script that could change the lightmap index for a group of meshes I'd much appreciate it.