WebP (still & animated) support
When exporting from for example After Effects, I'd like to take advantage of the newest formats to cater the needs of my co-workers and ensure the best quality. This includes being able to make life easier for the developers with more flexible formats like WebP and WebM. WebP is very versatile; it allows for a 24-bit transparency coloring, which is something other animation formats simply do not support (and formats that do support it, are not supported by web browsers).
Supporting WebP would solve this (for stills, but also for animation). Animated GIFs don't support the same level of transparency, which deminishes the flexibility (since it requires you to select a matte, which is only sporadically desirable).