What this still means tho is that textures, models etc all get dumped in the same directory and so you have to have a good idea of what files came from what addon if you want to modify or remove them. Here's an idea that may or may not be feasible, and may or may not be easy enough to impliment to be worth the effort of the programmers.
Feature request:
Introduce a new option for celestia to load files from different subdirectories of an 'addons' directory in a specified order, where the directories can simply contain the files from a single addon (or any combination of them that the user sees fit to make). This could be done initially with a config script containing a lexical listing of the desired directory/addon names, but perhaps later a 'launchpad' or something similar could be designed that listed the available addons and allowed you to check or uncheck the names, and/or change their order of priority.
This would allow addons to be installed (if the user wishes) as autonomous packages, kept separate from the default files for further tweaking etc, and allow the user to specify which combination of these packages to be loaded each session.
The lexical listing would allow multiple versions of files designed to fill the same role (such as 'earth.png') to be kept, and then loaded or not by specifying the priority of the package/addon relative to the default files and each other (also, thereby bypassing the problem of same-name files).
This system would be completely backwards-compatible with the current one - you could still manually add files to the default 'extras', 'textures' (etc) directories and have it all load up as one just like now. The only difference would be the addition of a config script (which could be empty or absent if users wanted to stick with the current system) and the extra folders.
Folder structure would look something like this:
There might be other benefits to this (such as the ability to quickly isolate the addon which is making your system crash, for example), but there might be some problems, such as an extended amount of directory searching at startup if there are lots of addon packages. I just like the idea of being able to selectively load what I want to see without having to pick my way through a hive of ssc files, trying to remember what's responsible for what. It's the sort of user interface enhancement that might make the program less intimidating for the average user.
Thoughts?