Tommy: Framewise, the cast ISN'T supposed to be able to grab the edge, and if they do, MK has a big enough frame advantage on everyone save Pika and Tethers to safely get away or get onstage from that position. Grabbing the edge as almost anyone in the cast is generally not an amazing solution to the planking. Seriously, how good of an answer to planking, is grabbing the edge, when MK can now safely return onstage? You now basically have forced yourself into a position where MK is onstage and you are on the edge (which SUCKS for most characters to have to deal with), or if MK doesn't want to do that he can get onstage and then start to run to the other edge.
Quarter Circle edgesnaps? Those are pretty easy to do, but the bigger question is why someone who is planking is required to do something like that lol. As for his Sword, yes it has that priority, but it's rarely an issue with projectiles to begin with. Most projectiles you can grab, hit to destroy, or hit to smack away regardless of what priority you have. Him having that priority on his sword attacks is not that big of a deal.
There honestly are NOT that many "solid" projectile choices in stopping planking. That is the sad, sad truth, and I'm not gonna tell someone "Oh yeah no that will definitely work, he's sooooooo vulnerable" when it looks clear that something shouldn't work. Sure, maybe the planker gets tired and makes mistakes, but what does this suggest? Fault of the player, or the projectile actually working?
Gyro... it's ok. Z dropping it doesn't change much. In fact you could argue that it makes it easier for MK to try and catch or swat it away since it travels at him slower. To Z drop stuff effectively, you have to be vertically over MK. Which can be very risky if you miscalculate and he just comes up and swoops at you or gets back onstage for free while you are basically mostly above him. As ROB, not a very pleasant spot to be in. As Diddy, it's not incredibly bad but he would rather stay grounded where it is safer.
Bananas in particular are just kinda meh at stopping planking. Two BIG problems it has are that like I said, they don't do a lot of damage (especially if you are just throwing them and they get stale) and that they don't have the knockback to try and kill the planker. If the Bananas had at least 1 of those qualities, it could be redeemable as a good anti planking projectile. But it doesn't. If the planker gets a stock lead, Bananas won't do CRAP for you. If you have a lead stronger than 30%, you will have to hit with a quite a few of them to even think about getting the lead back. All the while, MK having a plethora of options to deal with them.
YOU SHOULD BE AFRAID OF MK PLANKING YOU! Framewise it is extremely strong, strong enough that without any kind of restrictions put in place, he is ban worthy. Hell, something is wrong with you if you aren't at least appalled at how strong it is.
I also read those rules. You didn't specifically mention planking. You said Stalling is banned, but not excessive camping. Are you gonna make a judgement call whenever someone says "Hey this guy is planking/stalling" "No, I'm just camping really hard"?