It doesn't really matter that Jiggs and Kirby can edge guard Ness if they're not going to be able to get him off stage in the first place. He walls them out with disjoints better than they can to him. The angle above them that he camps is a blindspot that they can't hit. Then, he can space out an fsmash, and kill them at 60% since his tippered fsmash is like, fourth strongest in the game. Also, getting him off stage is one thing, and edge guarding his recovery is another. Just "jumping into PKT" is easy against a scrubby Ness, maybe, but a good Ness will mix up their recovery distances, fading in and out, and using magnet to stall so you can't really guess where they are recovering. And if you guess wrong, and get to him too late, you risk getting hit by PKT2 during his 7 frames of invincibility, or letting him back to stage before you.
As for going even with Roy, Ness forces Roy to approach, since crouch cancelling PK Fire is bad. Sure he can dtilt the bolt, but that still activates a pillar and resets the situation. Ness' aerial mobility combined with b reversing/wavebouncing magnets into b reversed/wavebounce PK Fire make avoid PK Fire a lot harder than it needs to be. Plus, if Roy decides to throw out an aerial near a dash dancing Ness, pivot PK Fire is going to catch him. So Roy is forced to keep the pressure on Ness and basically trap him in a corner. If he can't do that, the MU becomes really hard for Roy. Ness still has a CG on Roy and can combo him easily to 80 percent off of one grab, and edge guarding him is as simple as just jumping out and throwing out a magnet rising nair to regrab ledge then drop nair. It covers almost every stall option as long as you time it right. Or you could just dsmash if he doesn't sweet spot. Also, his dair isn't CCable and it comes out on frame 6. On the flip side, Roy has great edge guarding against Ness in that all he needs to do is charge B if Ness is below the ledge or he can just jump up and counter. He has DI mixups on his fthrow and dthrow that can lead to an fsmash at low percents and he juggles Ness decently well.
As for Lucario, Ness doesn't need to approach. His 6 frame dtilt stops almost everything Lucario can do. I played against Searing Arrow, a solid Lucario player from MD/VA and I baited out approaches, and then just CC dtilted into a combo string. If he started to get something going, Ness' 5 frame nair combined with his decent weight get him out of a lot of combos. And Lucario has a hard time dealing with a raw yoyo blocking his path or edge guarding him.
As for Aki's list, I agree with a lot of it. But a few notes. Ness has a hard time dealing with shield pressure, so he needs to prevent it from happening in the first place. Good luck doing that against Wolf. Falco's lasers mean almost nothing to Ness. He's far and away the easiest spacie to deal with IMO. Zelda is in no way 55-45 Zelda. At the ABSOLUTE least it's 60-40 for all the reasons I stated earlier. I also think Peach is a hella hard MU that requires the utmost patience, but I think her punish game on Ness is just too good for it to be even.