LunaPaint has the basic framework in place.
With a few modifications it could support Load Multi-Image, Add To Multi-Image, Export Multi-Image. That would allow loading frames from TIFF images and selectively displaying them or exporting them. Multi-Image functions would also work for icons or animations.
Export one frame and Export frames was meant for saving animations. But it could easily be expanded to support Multi-Images. A Multi-Image is my classification of a File that can contain multiple images such as an icon, or tiff file, or an animation file.
If we add a new Cycle Gadget in Export Project just under "Datatype" called "BitDepth" and set the values to 8bit, 24bit, 32bit we could integrate BitDepth Conversion and Color Quantizing at Save Time. The conversion takes place just before saving the image. It might be nice to add a ProgressBar at the bottom of Export Project. Just a few nice additions. It has great potential as a paint program.