Jiggs has no unwinnable match ups against anybody and its total nonsense to even suggest so. I doubt she even has any 90-10's.

What I think escapes many people here is that project M is based on melee (inb4 durr hurr the m doesn't stand for melee). In melee, the characters in the top 8 (or 7, really) have a wonderful and healthy meta game amongst them. All characters are represented well and all share instances of dominating the other characters, meaning there really is no clear superior character within the top 7 (there are current arguments against peach but I think that's more people taking armada's word as law rather than with a grain of salt, the gods are known to sometimes say silly things. Not saying what armada said was silly but there's always the possibility; peach has proven herself over and over again) Yes fox is the highest tier but at that high level of play its more dependent on the player playing the character rather than it is the character itself because of how deep the game is.

In melee, jiggs has proven herself over and over again to be a competent character with good enough characteristics to be a contender at the highest level of play.

Point is melee top 7 is a very, VERY good basis to try to emulate if one is to create a melee-like sequel. That's what the PMDT wanted to do when they began creating project m. All of the top tier melee characters are fundamentally exactly the same (with the addition of some new brawl tech). Fox and Falco got a tiny but needed nerf but they still function in the exact same way. Marth, peach, sheik, and falcon also function identically. Likewise, jiggly puff functions in exactly the same way.

My question is, if jigglypuff's character design is tried and true and proven to work efficiently at the highest level of play, and the redesigned project m characters completely overshadow her to the point of her being considered practically unviable, why is your knee-jerk reaction to buff jiggly so she can compete with these new characters? To me that just doesn't make sense. These new characters that HAVENT proven their competitive balance and character design should be tweaked to allow jiggly to be as good as she was before.

And for the record I don't think jiggs is nearly as terrible as people make her out to be. It's like a huge hive mind thing where people kinda just regurgitate whatever a notable player says until it just becomes common knowledge. I do think many PM characters have too lenient frame data and options, but it's nothing overbearing that jigg's can't overcome. To respond to your OP, I think the dtilt and dsmash changes are decent ideas (although instant dsmash is way way too much. Maybe 3/4ths of the startup time it currently has). Your first idea is the definition of why people complain about pm jank, to put it bluntly. It wouldn't fit at all with her toolkit.