At the risk of getting shot down but just going to throw random things out there, warning i really have no idea what im talking about really:
having the option for lossless compression (something like PNG), for previewing work files pre-compression losing quality (even w/cross-frame compression? no idea how realistic this is), but also the option for lossy compression (something like DDS) to further reduce filesize if necessary would be nice, as currently EFFs have the option for both. Maybe kind of ties in to setting compression level on creation, I guess...
Also, in a similar vein, maybe a tool to batch-convert existing EFFs to such a format for efficient transition. (this might be a given, Iunno)