I don't really think it's worth the effort to design a way for this to work, who need to compress BLB or BLS files, they're text files, they're so small compressing them would just be plain silly. BLB files are probably only 7/8kb max, and BLS don't even get transferred to the client (Or do they?) they just get loaded from the server, or something (I'm not very familiar at all to how blockland saving works), but anyway, they're too small to worry about.
And you don't really download DTS or DIF files all that much, unless you're on a server that's testing a new map/mod.