For what it's worth I must disagree with the notion that Zack plays the MU badly. He could play it better of course but in the VODs you showed of him playing the matchup I feel he lost the one game to Solar due to a lapse of mentality (not to mention Solar was actually playing fairly well and making some good calls. Zack was underestimating him that game 2) and Sage due to a tech error. I don't see how he is "garbage" at the MU regardless. He doesn't recklessly challenge Ness' aerials, plays around the grab well and is very very careful around Ness' shield. He has the knowledge, the mistakes come because as you say he is generally aggressively-minded and is more prone to overextension than someone like 9B, as well as often failing to edgeguard Ness properly.
FWIW He went 3-0 against FOW at ZeRo Saga but he was actually going toe-to-toe with him, FOW wasn't really running away with it.
I love the set of FOW vs 9B. 9B played the matchup better than FOW. He was just out-neutralling and out-footsie-ing FOW consistently and for the first two games FOW was just getting hit by everything. The thing about FOW is he doesn't play character matchups and instead focuses on player vs player mental battle and makes his opponents crumble by fearing Ness. That's what I see in the way he plays anyway. He does generally come unstuck when he fights mental fortresses like ZeRo, Dabuz and often Japanese players. He just wasn't respecting Bayo enough and 9B was definitely respecting Ness, although not excessively so.
Just want to play devil's advocate to your later point while I'm here. It may be hard for Ness to level against Bayonetta if Bayonetta is playing properly, but there is of course also the slim chance that the Ness is playing properly too! Crazy! If Ness gets a lead how does Bayonetta take it back? Her best chance would probably be going for a gimp, but if Ness has a lead she's clearly taken a few dangerous hits, is mentally shaken as a result and probably lacks the confidence in the gimp. And if you hesitate, you die instead.
Planking doesn't really work on Ness either. I know there was a discussion on it a little while back but I don't know if that was ascertained or not.
Not trying to say Ness is a counter to Bayonetta or anything, I just don't agree with your assessment of Zack vs Ness wholesale. To be fair 9B plays it better, but Zack doesn't play it badly by any stretch and there are some useful conclusions to draw from his play.
I agree with what I think your main point is though. Generally I encourage everyone to not jump to any conclusions based on Zack vs FOW or Pink Fresh vs Gonzales or whatever.
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I also agree that edgeguarding Ness is super important and people do give his recovery far too much respect. You usually want to wait until he commits to his double jump, PK Thunder or an airdodge because if he hits you with an aerial he'll probably make it back and could reverse the situation. If you make an offstage presence Ness will be scared and will go into "panic PK Thunder mode". When he's this scared you'll know when the PK Thunder and/or the double jump is coming because he will be wanting to get back to that ledge as soon as possible and he knows his recovery is limited. But most important is to have faith in the gimp. Ness' recovery is not very flexible at all and extremely vulnerable. If he's recovering diagonally up (most do), airdodge through him, any other angle you will probably have enough time to hit him before PKT2 if you've established an offstage presence and are confident.
Obviously his double jump is pretty free offstage too if you stay out of range of DJ Fair. If you hit him out of his double jump you can basically guarantee he will go for the easiest PKT angle.
Have confidence, don't hesitate and it's really not that hard. Play to learn, don't play to win all the time.
You now have no excuse. You're welcome.
3-2 Sandstorm 
