I am not an extension developer but it's a rare month when I don't find myself popping open an .xpi to make changes to the JS and HTML for personal aesthetics; or bugs only I have. Temporarily loading extensions is not a solution. They say they'll be producing an "unbranded" non-walled garden version that for technical users but no such build has been revealed yet. And if they do make it the unbranded version won't be in my OS repos.
This walled garden, the addition of Adobe EME/DRM, the bundling of "Pocket", and the incoming drop of XUL based extensions are too much.