I'll take a crack at this one
@Goku9001.
I agree with this, however I don't believe Piccolo needs to be that far below 50% Goku to satisfy this. Piccolo knew 50% Goku had no chance against Cell as Goku had already established that after leaving the RoSaT. Piccolo is also smart enough to understand that Goku's 50% display wasn't his full power, so even if Piccolo got close to that level, he should know that he would be useless against Cell. I've always had Piccolo = 40% Goku which I believe works with the implications.
The main takeaway is that Goku isn't believed to be that far off from Cell whereas Piccolo is completely useless. It's more comparable to Vegeta vs. First Form Frieza where even Gohan and Kuririn, despite being significantly weaker than Vegeta, were still capable of contributing towards the fight. Here, Piccolo is a complete liability and isn't worth considering even if his role is support. Even with the expectation that Piccolo knew that 50% MSSJ Goku wasn't necessarily his full power, it couldn't have been too far off base. For Piccolo to be a complete liability would mean he should be multifolds weaker than 50% MSSJ Goku.
The problem I have with this is Cell immediately instructed the Jrs to make the Z Senshi feel pain, or even kill them if they wished. We see that all of the humans were swiftly beaten until they were unconscious, and yet Piccolo is seen fighting back on several pages, let alone the chapter cover page where he looks like he's somewhat competitive. Why would Piccolo still be in relatively good shape if the Jrs had no problem nearly killing the humans? There's also the fact that the strength checker makes it clear that Cell isn't 100% only saying that Vegeta and Trunks were holding their own, there is some ambiguity there.
Not really. We've already established that Piccolo is weaker than 50% MSSJ Goku let alone Vegeta/Trunks, the exclusion of Piccolo makes no sense in this context if Piccolo was equal to Vegeta/Trunks, and Cell's assumption of Vegeta or Trunks being the warrior Goku was talking about already sheds any doubt as to whether or not Piccolo could compete with the Cell Juniors. There is no logical explanation for Piccolo to have fared just as well as Vegeta and Trunks unless the Cell Juniors were holding back and having fun with him. At that point, how much they were holding back would be arbitrary. Nappa aimed to kill the Z Senshi despite being suppressed so I don't see this as a proper counterargument here.
This is admittedly the hardest one to hand wave. I've always looked at it as Vegeta only having interest in fighting/beating the Saiyans. Considering how hyper-focused he was on Goku during that day, can we really say with confidence that Piccolo was on his radar?
It's impossible to handwave. You would legitimately have to believe that Vegeta is retarded and doesn't know how a tournament works and judging by his smirk when he miraculously gets to battle Goku in the first round seems to imply that he was aware of the possibility of battling other competitors.
Can you expand on this one?
Goku and Vegeta only believed Kibito and Kaioshin were potential threats during the tournament. Gohan seemed to agree with this but didn't believe Super Saiyan was necessary against Kibito despite believing that Kibito and Kaioshin were the strongest in a tournament including Piccolo.
This one is an odd one because even though they understood that the Saiyans had the most power, they were also confident that Pui Pui would be able to beat them, along with Kaioshin. The Z Senshi were all suppressed to 0 so I'm not sure how much we can really take away from this when we saw how clueless Babidi and Dabra were later on.
I believe this is one of those debates that will be around forever. Both sides have inconsistencies that have to be written off to suit their own argument. Looking forward to seeing what you have to say.
Babidi and Dabura had to have based it off of some other metric because regardless of whether or not they were suppressed, they knew that the Saiyans had to be capable of filling the Buu meter and that was before Super Saiyan was revealed to them. The only thing that this suggests is that the Saiyans power was far too large to be comprehended which is implied by many of Kaioshin's reactions within Babidi's ship. For Babidi, this was revealed the moment Base Vegeta absolutely trounced Pui Pui.
