A lot of mail clients, especially in B2B, have policies in place that disallow external images and media to be loaded by default. This in result "breaks" most layouts that depend on images to load. Adding an option in file Manager to embed media instead of just linking to it would resolve that issue. Or maybe, as I have seen on similar tools, a selection box on template-level where you can choose the media loading type: "Link Images" - or "Embed Images"