Well, there are a few problems with the add-on system, for example, the fact that the server uses the zip filename, it should use the name that is inside the info file, this way, the renaming problem is gone.
Also, blockland should keep a small database of all files downloaded, together with the checksums, to make sure, no add-on is downloaded two times, that wouldn't be so hard.
I think when RTB 2 is out we should stick to it when it comes to add-ons, just join servers with RTB2, this way we can also see what add-ons the server have.
Let's just wait, things will clear up over time :)