The reason we ban WW and ANY item in vBrawl play is because people hold the notion that random events == bad, 100% of the time most of the time. People who play or endorse ISP fundamentally reject that notion, so applying vBrawl logic to ISP isn't helpful.
Ganon is either bad or good by random chance... So? That's an inherent part of the format, as well as Ganon's character design. That makes Ganon a high-risk, high reward (well, marginal reward, because he's still not THAT good) character, and ISP accepts that. Either way, if Ganon is THAT bad of a problem, we DO NOT BAN INDIVIDUAL ITEMS TO FIX IT. Either Ganon, flaws and all, is legal, or he isn't. We don't just ban every single item he has an exploit with, unless EVERYONE (or a 51% or higher majority, at any rate) has that exploit, too. Example: the Green Shell. It's not banned because Ganon can do dumb things with it, it's banned because EVERYONE can do dumb things with it.
Now, you're also asserting that everyone has dumb things with Banana Peels, but let me ask you this: if that's really the case, how come EVERY vBRAWL DIDDY MATCH doesn't just devolve straight down to infinites after the first peel spawns? If they're THAT good, then Diddy's should be getting #1 finishes left and right, just like the ICs SHOULD. But, practice =/= theory, and in practice, games don't devolve to "camp for the peel -> infinite -> ??? -> profit!" every time, most of the time, or even SOME of the time.
Even if they did, that'd be a reason to ban Diddy, wouldn't it? That's the main point of contention I have here. I read your posts, Grim, and I NEVER hear you spearheading a "let's ban Diddy because he has broken infinites" campaign. Why is that? And, if you don't think his bananas are that broken in vBrawl, where he has a literally infinite supply of them, why are they broken in ISP? Because, POTENTIALLY once in an 8 minute match someone MIGHT, maybe, possibly get a peel and get one stock off due to an infinite?
TL;DR: Unless we start seeing this problem pop up in tournaments all the time, we have no reason to ASSUME that it will. Items stay legal until they are PROVEN to be broken, and if the only thing that makes ISP nanas broken is that anyone could get one, then they aren't broken enough to ban... yet.