Answered *half* of my own question! The stainless pin provides very little more resistance to drilling than brass. 5/32 DEWALT Titanium Nitride Coated shank bits and a cheap $30 cordless driver had no problem (raining and too lazy to get my good tools from work van). I butchered the bushings just like my first build, but that's simply my lack of skill lol. I'm waiting to receive a set of new 2.5mm bushings before I re-assemble. Crossing my fingers I`m able to peen the stainless pin just as easily as it drilled out.
So far I found little to no difference in working with the 130mm versus a 91mm. Other than maybe getting the last pin lined up in the liner hole, but after a couple tries I rounded off the pin head with Dremel and it went in just fine. Disclaimer: I only removed the opener layer and put the outer liner against the saw. In doing so, the saw did come off it's spring but I found it quite easy to replace (even easier than 91mm). I did not attempt messing around with the knife layer. Something tells me that could get tricky?
Meanwhile I did the "bit driver" mod while the scales are off. I used the chisel on the Cybertool L/41, it fits each hexagon side almost perfectly. Slowly rocking back and forth I poked through the red plastic of each inner side. Then I used an Xacto knife to cut out the black grip from the outside. At this point it was close but wonky shaped and too small to fit a bit. So I put a 1/4 bit in vice grips, heated up the hex side of the bit with a torch lighter, and inserted/melted into the hole to form a perfect hexagon. Detailed with the Xacto again and it looks real nice.
When finished I`ll update how the stainless peening went for me - the most important part.