Not going to add a feature, but it's easy to leverage PKHeX.Core to do things for you.
string result;
foreach (var file in SaveUtil.getSavesFromFolder(path))
SaveUtil.getVariantSAV(File.ReadAllBytes(file)).dumpBoxes(path, out result);
Feed a path to it and it'll get all the save file paths, then dump every single one's boxes to the same path.