"...Savable file format that preserves working layers, text layers saved as text for easy re-editing, advanced layer effects, full history tree with history brush, all sorts of filters, file sizes and resolutions above chipram size, and the list goes on...)"
ImageFX...
In general there are also other Amiga programs out there that have those features but I've only tried ImageFX. For most to be usable professionaly you'll need to have a top spec Amiga though.
