That's funny, I feel like you literally just watched me in the lab.
I've been experimenting with the PK Fire thing you mentioned, trying to see its applications in real matches, mostly for edgeguarding. It's been a bit... unsuccessful so far, but I'm working on it. I was going to make a video of this tech until I decided I should determine its overall usefulness first.
I've dubbed it the Fireslide so far. Running at the edge, and turning around with PK Fire will allow Ness to just drop at the ledge. Add an aerial like bair, or fair, and you can get quick aerials right below the ledge (where a lot of people recover).
The second one is something I've been doing since Brawl. I call it the PKT Ledge Stall. I was a bit reserved with bringing it up since ledge invulnerability was changed in this game, but it's proven to be useful in this game, at least to me. As you said, DJ off the ledge, instantly PKT, and curl it into the stage for an attack that will hit opponents right above you and reclaim the ledge. Just be careful with it, as there are risks.
I just did some testing with dtilt actually, and I've got some promising results I'd like to report to the Ness community. You might just see dtilt in a slightly different light. I have my first day of classes tomorrow however, so I'll post the details probably after then, since I need rest now.