This is the project of my collegue Gideon.
As I understand from him 1581 is impossible with the current hardware/method. 1571 maybe. The ram that holds the image is rather crowded already.
I have a prototype here connected to my 128DCR (the idea is I implement the software control IEC drive, so it can be used on plus/4 and such that have no compatible cartridge slot). I can tell you it sure is fun to see it work. Sadly it is not yet flawless on my 128dcr. The proto I have does not have the audio circuit mounted so I miss the emulated drive sounds.
When this project is finished it sure is a must have for any serious retro gamer as it solves the problem of dying floppies.