Personally, I think keeping most or all of charge on death is fine for these characters. Those charges function in a way that is completely different from other types of charge attacks (except
maybe you could consider Ivy's to be more "normal", but it takes so long as to be simple to consider distinct). They charge over a long period of time, instead of over the course of a few seconds. They should be treated differently.
So I missed most of the talk on wario's fart, but I agree with the sentiment that waft is a bit thoughtless, considering how there is no interaction between him and his opponent in acquiring it, plus keeping it on death. The choice between recovery and killing with is interesting, but it's not emphasized enough. Considering he has pretty good kill potential, and with his weight, aerial drift, decently sized and positioned ledge grab boxes, and the high risk in something questionable happening with engaging his up b, usually leading to a stock being lost from his opponent, makes his recovery fairly decent, so it just feels like isn't really needed.
It needs an adjustment, that much is certain, but in what way, I'm unsure of atm. I'd like to see more debates on the matter, differing opinions are welcome.
I think the real problem is that there never needs to be much risk in using it, since he has some pretty good setups/50-50 mixups into it against many characters, and getting it is literally just "sit around for x amount of time" instead of a reward for some kind of play, or an active charging, or anything like that. You're right - it's pretty thoughtless.
In Wario's case, I feel like losing charge or losing partial charge on death would make it more thoughtful. Especially if it became more useful for recovering. Instead of "I can
maybe make it back with this, or I can keep a really good killmove for next stock" it becomes, "I can use this to make it back, but I'll have to wait a bit longer to get back my really good killmove." Either way, you have to wait to get your killmove back, so it might be worth getting more damage with your stock. If it fails, it also feels like you've lost less, since you're losing x% of a charge, instead of an entire charge. That becomes a more thoughtful interaction.
On the other side, I feel like Waft is kind of boring overall. It's kind of funny, I suppose, but it really boils down to a really powerful and large killmove you get for free every couple minutes, with guaranteed conversions or 50/50s into it on a lot of characters. But before full charge, Waft is pretty useless. You're going to use that move a few times a game at most. There's no reason to ever use it before full charge. There's no reason to ever
think about it before full charge except "hey I should camp a bit to let Waft charge" or something.
It's almost certainly the least thoughtful or interesting long-term charge. Ivy has to work for it, charge it up using specific moves, maybe use moves that wouldn't be as optimal if she didn't want charge, for that tradeoff. Lucario has lots of decision-making tied into aura. But Wario just
plays the game until he gets Waft and uses it to kill. I dunno, it just seems like it could be more interesting.
It's be really neat if Waft actually did
something before full charge. Maybe if you hit with a few of those somethings then you are rewarded with a full charge for it, I dunno. But right now it just seems lackluster. Wario is a pretty interesting character overall, and he has so many mixups with so many of his moves, especially his other specials, and then there's Waft, which pretty much just has one practical use that you charge up just by
existing.