I am going to put this aside for a while in hopes it will age like a fine wine.
There might be some way to trade a little space for a lot of time, or to do any processing where it won't affect fling speed.
In any event, some things must happen before we can do anything. The most important is finding a way for CC to know the column setup for all the connected-to libraries, not just for individual books. This requires coordinating calibre and CC, and requires some small API modification in calibre. Once this is done we will be able to have column pick lists and metadata, obviating the need to (for example) manually type the grouped custom column definitions in settings.