It occurs to me that a modification of my really old and mostly useless "Jack" program might be able to do this. It's essentially a front-end that creates a batch file to encode a collection of track01 track02 etc wav files. Since it assumes the WAV files are already there, I could in theory rewrite it to do a single LAME line for all WAV files instead of one for each.

The odds of me getting around to it are rather slim, though.