This might be a totally useless contribution, but it occurs to me that you might be able to short circuit the fact that these programs are searching all files by changing permissions so that they CANNOT search parts of the file hierarchy. In other words, do something like changing the group of the files they should be able to read to 'qpe' and make the permissions something appropriate, and then change permissions elsewhere so that they cannot traverse, say, your pocketworkstation debroot directory or something. Anyway, just my random 2 cents that may or may not work.