I like discussing this too, it feels fun and helpful (For me, honing some thinking/constructive arguing skills as well.) even if the idea doesn't get picked up. You make some very valid points on the idea of a Zelda "Deep Breathing" type of move, I've been thinking it over, and I thought of a few things:
On 1, there IS an interesting way to work around this, that would get rid of possible obnoxious KB issues. During the active period of this move, each normal receives some sort of damage boost, (Say, 2% or 3% for certain moves. More or less can be adjusted if these boosts seem to be off-balance.)
but its KB stats are adjusted down to make its KB match the un-boosted versions during the active period as well. (It would work similar to Shulk's buster art in SSB4, but with a little more polish. It might take a little more work to execute though, unless a fast-route is taken, like with Shulk's monado arts.) You could use the period mostly to try and get as much damage on your opponent as possible, but moves don't knock unnecessarily far.
Also thinking about it, the amount of time it lasts would be up for inspection, as I myself think 10 seconds might not be enough. Knowing how little that amount of time does for Wii Fit Trainer...
You COULD replace one of these boosts instead with a slight KB resistance increase. (Similar to one of WFT's DB customs, where she receives a temp weight increase. Only in this case not so drastic.) But, really, with any boost, it's gonna have some types of double-edged-ness. We want her to get something that could improve her, but there's always the possibility that it could be too much in some situations, so if we want it, we have to... Pick our poison, so to speak? I think getting this change would just need to take a little bravery as far as backlash for its design.
With 5, lol yeah. It's hard to be Zelda. I think people will complain about Zelda's design no matter what... Unless she was a mollusk...
But then we'd be down about her design... HA