Your arguments are incredibly vague and unconvincing. You basically say "time invulnerability perfectly" for everything. To start, that is not realistic. In my opinion the real trouble with planking is having to go off stage to fight metaknight, where you are likely to get gimped and he is not. Many of these attacks allow you to stay on stage (projectiles) and attack metaknight while he can't do anything except dodge and time ledge grabs. Eventually SOMETHING will hit him. As for the attacks that require you to go off stage, admittedly most are bad ideas. But for characters with good recoveries the situation is almost no different than fighting a metaknight in the air, it is hard yet possible. You are overestimating the invulnerability advantage given to the planking metaknight. If you properly time your offstage attacks between ledge drops, the only advantage metaknight starts with is he has better attacks (and a slight recovery advantage depending on your character). This advantage starts as soon as the player picks metaknight, though. So it holds no real argument in this thread.
I can't say I have experience seeing a link vs a planking metaknight, but to me bombs seem good enough to put him in the green. However, if you or someone else provides better arguments I am perfectly fine with changing it. All character colors were guessed with bias by me, so I am waiting for people to argue them for better accuracy.
I am reading the posts right now and will probably make some other changes people have pointed out.
First: don't put words in my mouth. I did NOT say time invulnerability "perfectly." Perfect timing is completely unnecessary; the window of safety is huge in comparison to the time during which MK can be hit, and sufficiently good timing could be achieved with only vague familiarity with the game.
MK has a huge number of jumps, and until he actually regrabs he is below the stage and untouchable (we'll deal with diving after him later). He can remain in that state for up to 6 seconds. With up-B, regrabbing the stage requires only about 1/10 of a second, and its hitbox protects him from most projectiles. To hit him while you are on the stage, you need an attack that gives the MK player less than 1/10 of a second of warning between when you start attacking/shooting and when the hitbox reaches the stage, AND it is strong enough to get through his attacks covering his return, AND you need to have the capability to repeat these attacks to maintain continuous stream of these powerful hitboxes at the ledge with smaller than a 1/10 second respite between consecutive hits for the full 6 seconds or so that he can safely hang out underneath the stage with his jumps alone. If not all these conditions are met, he can simply delay under the stage until the blind spot in the attacks arrives and then grab the ledge. The flame attacks, the closest things to this condition that exist, are so easy to see coming (the firebreathers have a second or so of lead in time), that punishing them is also trivial; upon seeing the setup, just up-B and stage roll, and you're behind Bowser/Charizard before the flame is even at the spot where you previously were.
Just in case my point isn't immediately obvious from the above analysis: the claim that spamming stuff at a MK using a ledgestall will
eventually score a hit just isn't true. All MK needs to do is watch for the window of safety between your attacks and regrab; it is so easy that for an experienced player the probability of making a mistake is nearly 0. And that is the
worst case scenario for MK. If the attack requires you to be near the edge, MK can usually also punish you for even trying, if he feels like it.
As for going off the stage yourself, as noted before, MK doesn't need any advance warning to regrab the ledge - to catch him in between ledge grabs, you would need to go from sufficiently far on the stage to be safe from MK to being off of the stage and starting to attack him within less than 1/10 of a second. No character is that fast. As a result, MK
does get an invulnerability as he starts his fight with anyone who dived after him, if he thinks he even needs it.
You don't see videos of good MKs ledgestalling against Link because it's not necessary - even on the stage the Link boards decided the matchup was 20-80, IIRC. In casual play I have had the dubious honor of seeing a ledgestalling MK, and with the slow traveling speed of Link's projectiles, no amount of trying to fake out MK's timing would help - he just watched the projectiles and regrabbed in between. For reference, that player had just picked up MK a half week ago.