There were possibly 2 theories he could be referring to. I found neither of them to be extremely impactful after long periods of testing though, but here goes anyways.
Earlier I was messing around with dtilt. Dtilt has a 25% chance of tripping, and off the trip you can combo into the bat. As such, using it twice gives you a 50% chance of tripping, which isn't bad. Turns out you can use dtilt twice without ruining the trip because if the first dtilt trips, the second one will go UNDER most characters' trip animations, and if the second dtilt trips, you're easily able to follow it up. Either way, if the first or second dtilt trips, you STILL have time to combo into the bat. While it is possible to shield between the first and second dtilts, it would be a hard reaction for opponents considering how fast dtilt comes out. Dtilt also has very few recovery frames, so it's a bit safer than grab. This dtilt trip into bat combo gives Ness something that he currently lacks: a good method of KOing people in the direction he's facing. However, you have to be FAST with the bat follow up on the trip, so fast that you can't really react to the trip, you've just gotta try it and hope it tripped. Also, nothing changes about dtilt's awful range. Overall, while it seems good on paper, I wasn't able to make too much use out of it, so I didn't really bother mentioning it.
The second one was this PKF turnaround I was playing around with. If you dash at the edge and PKF in the opposite direction RIGHT when you get to the edge, you'll turn around and fall off the stage. I was thinking you could use this to stage spike people who are recovering low since this gets you REALLY close to the stage when you fall off. It also allows you to use fair to stage spike, which is multihit, therefore a bit trickier to tech. What holds this back though is that you have to do it out of a full dash. Most of the time, opponents won't recover below the stage if you are at a dash distance from the edge anyways. I never found a consistent use for this one either.