But the traffic overhead even if it would be enormous is on the USER side! Hell, even if I transfer 300 kb/mod instead of 100kb it would still hurt addon sites less than transferring a zipped 80kb file + webpage.
Tracking is _not_ cost intensive (ask the guys at piratebay...) and could even be done decentralized via DHT.
However if you've already even talked to the BT-Devs themselves and ditched the idea, maybe it's better for us as well too look for other alternatives instead of trying to force people down the torrent-road...
What about small "patches" to existing addons instead of always downloading the whole thing?