In order to be inclusive, in principle all submissions would have to be accepted. This could create an issue where it becomes difficult to find resources that are tested, proven stable, and discover which ones are more widely used - as all get lost in a sea of submissions... Looking at what has been done by other large-scale open source projects, who have user-submitted plug-in libraries, here is what is known to work well:
1) Resources should be classified using user-defined tags - these tags can be added, deleted and searched by all. Over time, this creates self-defining and self-curating categories: they are inherently useful to users, and require very minimal intervention and culling from administrators.
2) There should be a compatibility rank: when a plug-ing/extension/library is added, users should be able to download and instal it, and then RATE it, as to whether it is compatible with their setup, or whether it has conflicts (either with the bare-bones IDE, or with other extensions and plug-ins). Note, that this is NOT a ranking based on features and functionality, or on how much a user "likes" the resource - it rates ONLY its compatibility with their instal and configuration. This creates a self-curating system of resource compatibility.
3) Resource (plug-in, extension, library) developers should have their OWN product page, which they manage in their own domain - not within the resource library itself. The resource entry in the library should have LINKS to the resource's home page, forum, guide, issues, etc. (if available), but these should be held and managed by the developer themselves, in an external domain. This reduces the amount of resources the project has to make available for plug-in developers, and means that plug-in content (such as content in discussion forums and issue trackers) has to be curated and maintained by the developer themselves.
4) Users should be able to search for/instal/update/uninstal the resource from within the product itself - this reduces the number of steps the user needs to find the resource they need, and has a huge impact on adoption of the plug-in system overall. This also makes it easy to track how often plug-ins are being installed and uninstalled, and creates self-updating usage statistics.
I hope these suggestions help - I'm sure others will have many more.