no worries, it's a rather unsual and not very urgent request I guess (and yes I am aware that changing the code breaks the as soon as I update it) ^^. Thanks for your answer.
Ok so the main thing I was missing before was the line in the gui file to change the cursors appearance. Now the eyedropper works with shift which is already very nice , but the alt key still gets intercepted by sprytile and my usual hotkey does not work.
Additionally I had to add
if event.alt is True or event.alt == 'PRESS':
in line 802 in the handle_mouse function and I've also added myself a new case in the gui.py file to get a different Icon (from the already implemented ones) for alt.
Thanks very much, looking forward to doing with sprytile now :D