I guess my problem is similar to my problem with the new extensions model for Firefox. It might be much smoother for 95% of developers with the new API&#x27;s. But the remaining 5% of cases go from &quot;pretty hard&quot; to totally impossible. With Bukkit&#x27;s API, something like buildcraft&#x27;s pipes with all its appeal would have been impossible. Or the only reason something like tree style tabs is going to be possible with the new fx extensions API is because it already exists so they know they need to make that possible. If Buildcraft or Tree tabs did not exist from the fully open ability for an add-on to modify their host app, I find it unlikely the APIs to support them would ever exist.