Just lurking… But FWIW here’s a few quick observations before off for some tasty IPA. Highly recommend watching all the RARE GDC vids on SOT as they’re amazing. Done a fair bit of tweaking this kind of platform / player movement gameplay before, and often its a PITA when it should be so simple. As you can often find yourself fighting the CMC, especially in multiplayer. 
Anyway irrelevant of whatever CMC settings you tick, and irrelevant of whatever powers the platform (physics / kinematic), you’ll still need to manually add some kind of platform / player momentum imo. So while the impart velocity / impulse options seem like a nice idea, most of the time they never quite work out, or are never really that all reliable (just my experience).
So maybe try to work out the momentum required, and then factor that into a Launch / Add Force node or something similar (sample code for tether systems may also be useful to look at here). If so, skip using Launch. But overall tbh mostly ended up disabling jumping on moving platforms (ships). As there always seems to be a bunch of edge cases where it still fails.
Overall, this kind of thing could use a proper Marketplace plugin solution. Especially with Epic changing physics engines and breaking things across different engine versions. You may get something working today. But then when there’s another version it stops. Just my 2c… YMMV 