Thank you for your quick response!
After hours of searching I actually found an old Swiss Bianco video where he swiched the scales of a Midnite Manager showing the backside of the scales.https://www.youtube.com/watch?v=4dnNmXDMqzI
(intersting part starts at 7'20'')
So, my first question is answered
You can add a pen to a 58mm model. You need new scales (specific for pen), the push button and of course a ball pen mine. That's it. I actually saw one of the led units and I guess you cannot get them anywhere other than buying up used led models.
I am looking to upgrade my EDC-keychain and am wondering now which mini SAK to add...
At the moment it only has a Streamlight Nano (keychain light) amd a Dolphin peanut lighter.
Since I am set on having tweezers, toothpick, blade and scissors and for all the tools to be black, I am considering the Classic SD, Rambler and MiniChamp (modified by replacing the pen scale to regular black ones). What would be even more intriguing is a Vagabond but I cannot find them anywhere not even used on eBay.