Considering the vulnerable nature of the AUR, I think your use of the word “useful” would be better replaced with “critical”. Any tool that helps AUR package installation must incorporate security checks BEFORE installation. Even the YAY developers added basic security checks a few months ago. https://github.com/Jguer/yay/pull/2855
If you need inspiration, look at how popular the archcanary security project has become. Archcanary — a layered security scanner for Arch-based Linux