Here is a thought.
With your cursor mirrors, could you allow the cursor movement keys to operate on all the cursors?

I just wanted to add some characters to the end of a 100 or so lines of different length. It would have been really nice to drop a cursor mirror on all the lines, push the end of line key, and start typing.

Then you could do other useful edits with a column of cursors, for example left arrow back a few characters and insert something.

You would kill of the cursor mirrors and return to a single cursor with a mouse click.