I think this may be possible to do with the combination of an additional Pen Set in which the Pen Weights are made heavier, and Graphic Overrides. When defining Graphic Override Rules, when specifying the Override Style, you have the option to override only the Pen color, or both Pen Color and Weight.
But it would be best if you could post a few screenshots of the current state of the file and the desired state as well.
Loving Archicad since 1995 - Find Archicad Tips at x.com/laszlonagy
AMD Ryzen9 5900X CPU, 64 GB RAM 3600 MHz, Nvidia GTX 1060 6GB, 500 GB NVMe SSD
2x28" (2560x1440), Windows 10 PRO ENG, Ac20-Ac27