Can you remove a 'Personal Workshop' 'Power Counter' during an encounter with ICE?
Yes, Personal Workshop allows you to install programs/hardware during a run. You have already paid the click to host them though, so all its really doing is allowing you to defer payment until they are needed.

This does allow you to install a Femme Fatale after the corp rezzes and Ice, targeting that Ice for the special bypass, and then bypass the Ice as you encounter it that turn. Or to install a parasite on an Ice after its rezzed, and then immediately lower its Strength to 0 so it gets trashed using Wyrm/Datasuckers when you encounter it.