how about writing a macro that selects all wire shapes, reads the phase from the shape data and changes the arrowhead to "no-fill" for the phase(s) of your choosing. In the case where your phase names might not always be the same, you could have the macro query the shapes and build a drop down with phase names and select the pahse to change.
and I'm assuming you mean something like the attached for what the arrowhead looks like...
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