You know, the only use of API's is exactly to DEFEAT the requirement of having the decompiled core files...
I agree with that, hence why I expressly mentioned that I had no intentions of even trying to do so in the OP.
I'm mostly wondering if there's a way to save time - hitting "Build" then "Run" is a lot easier than running a recompile, reobfuscate, copying the plugin over to my full version of Minecraft, waiting for the launcher to load, waiting for the game to load... all just to check if the one liner I just changed makes that pesky NPE go away. Not to mention having direct console output in NetBeans rather than digging through a log file. (I'll admit half of this is a problem only because I'm really lazy and using Tekkit instead of installing the mods myself... )
That said, it's still not a huge deal to me, especially because the only way I can see it working is if a version of IC2 was released that referenced all the unobfuscated base classes instead of the obfuscated ones... and that just seems like way too much work.