For sure,
The DMI issue has been identified, so if that turns out fine, I think this is entirely good to go on the icon front.
The metadata itself should be fine as long as you respect the property for it. As an example, the bees.dmi icons for bees has
This is an ordered list starting at pixel (0,0) and moving across with each frame being 32x32
It is 100% safe to copy this metadata out, do whatever you want to the dmi as a png file, including rewriting all the metadata. Then just re-insert this property.
Audio is difficult as you described.
But I would say, yeah, lets do this.
#Edit#
OK, so probably should add, the property I am talking about is the compressed text metadata (zTXt). You can copy that directly and it will all just work, assuming the pixels 32x32 (or whatever) were not moved in some way.