I thought about trying to do mine before I ended up switching motors. If I were going to attempt it I would try heating the pulley and then pressing the shaft out through the pulley...
To reinstall i would put the water pump in the freezer for a day or so rose bud the pulley and then try and press it back on.
One could also go and have the shaft threaded at a machine shop and then have a pulley threaded to match (maybe not the stock pulley which would solve having to remove it).
Anyways good luck with it I went the easy route and swapped motors.