Need: Broken Model Explanation
This one is straightforward. Show visually or at least explain to the user what is causing their STL to be considered broken. “Integrity issues” is not specific enough. I find that many online 3D-printing services (Protolabs for example) offer instant, intuitive, and easy-to-understand explanations of their DFM analyses.
More Info/Original Idea: PreForm "Broken Model" Visual Mesh-Checking