I understand what you mean. Currently you can only animate spanning from the first to the last frame, but more control over this is definitely planned for future versions. At some point I want to create a timeline of sorts so that you can freely control at which frames objects are placed and animated at. But it's a bit of work so it might not make the next version.
Same goes for legacy ilda file formats. I want to support them at some point, but palettes is a PITA.

For now though, it's quite easy and free to convert your older files into format 4 or 5 using for example laserboy.