Currently the MIME database (include/mime.xml) is a static list provided as part of JAS. It would be handy if this list could easily be updated via the backend.
The question that comes to mind however is whether upgrade should overwrite a customized version. It seems rather annoying if you spend time to add your own MIME types that are subsequently forgotten when JAS is upgraded. Maybe adding a flag "custom" to the XML file to indicate it shouldn't be touched by upgrades.
The JAS backend should have a filter section to more effectively drill down in the data. the filters should be automatically generated based on the module (similar to the CMS). Text fields should have a inline dropdown with available values (like the search box).
Additionally it should remember the last set filters if the user comes back to the page later. This will require a "Reset" button to set all values to their defaults.
The JAS backend should support recursive delete options.
Note that this probably also requires recurseCategories / recurseContent to be submitted in the CMS. This is probably best done by setting use=form.