I'm still working in ArchiCAD 9, but my technique when doing framing plans is to stack two viewports in Plotmaker placing the framing plan on top of the floor plan. I change all of the pens in for the floor plan to gray. To my knowledge there is no easy way of doing what you want to do in AC9. A painful workaround is to duplicate the solid line type and change all your walls to that solid line type copy. Open up a new file, hotlink your plan into it, change the solid line type to a dashed line in the line type settings, create a new view, and import it into plotmaker.
I wish archicad had the "BYLAYER" option of AutoCAD. And it would be great if you could change the linetype of the layer based on layer combinations similar to how you change the layer intersection group number in the dialog box. My employer is a fan of dashing furniture and door swings etc. on the reflected ceiling plan, it would be great to easily dash the furniture layer in the RCP layer combo.
ArchiCAD 25
Windows 10