How to combine level sets easily?

[tensorpudding]

I am currently writing a bunch of utilities for handling Tile World files. I've already written one that creates DAC files without having to open an editor or write anything, and I'm soon going to start working on one that would "clean" a TWS file by rearranging the segments so that they don't appear out of order, and removing segments that refer to levels that don't exist, etc. A utility which allowed interactive merging of TWS files solutions into a single new TWS file would be interesting.