Thanks for your positive feedback; I’m happy to hear you’re finding MLA useful.
I agree it would be nice to add a “bulk edit” function to the new Media Grid. I will add your idea to the growing list of features I’d love to add to the Grid and to the original Media Manager. My sense is that this would take a significant amount of effort and a far greater understanding of the Media Manager/Media Grid code than I have been able to achieve. I have found wrestling with this code to be the most frustrating part of my entire WordPress development experience. I am always looking for more documentation and examples, such as this promising series just started by a really senior WordPress developer:
Getting Started with the WordPress Media Uploader
I promise you I will keep at it, but it is a long-term project and I do not know when I can add features like the one you propose to MLA. Thanks for your understanding, your patience and your interest in the plugin.