Hi, welcome to
1. If you want to adapt Wingman scissors with a 4.75mm hole to any tool with a 5.75 hole and want to do it ideally with radius shutter and perpendiculars of all hole planes, do not even think that it can be done at home. Only an experienced milling machine operator with carbide mills will help you. Apparently the metal on the tool is hardened.
A Dremel and abrasive or diamond grinding bits make this kind of mod easy. You don't need to be too precise with the pivot hole and there's little risk of breaking the scissors or the bit while doing it. Takes longer than using a mill or drill, but is more controllable.
While I applaud the work, and think it's great that you're making the tool she wants, I am seriously confused as to why you'd make these changes. The scissors on the Wave are flat out better than the ones on the Wingman. They are just better at cutting a wider range of materials quite well, and even with materials that both cut well, the Wave always cuts better.I think people get caught up on the length of scissors, not how well they actually cut. I think, maybe the only advantage the Wingman has is the thumb pad to push the jaws closed is a little more comfortable.Here's the thread where I tested all the scissors I could find.https://forum.multitool.org/index.php/topic,36798.0.htmlBut again, having the tool you want is better. If your GF's sister is happier with the tool modded, then she's more likely to use it, value it, and spread the good word of awesomeness of multitools.