It is best not to change the first row of pens IME, as GS uses a lot of them for their parts as you have found out. Unfortunately, they also use a scattering of other pens for their parts too, so there is no hard and fast rule.
I would suggest you change your thinking a little - keep the top row of pens (and pens 91-100) as is and use dedicated pensets to map them to the colors/thicknesses you want for output.
Try reading some of the Pen Standard related discussions such as the ones here
, to suggest but a few.