Rizen
Let me break down your post (which is in the spoiler. Don't ask why) little by little again and add some extra inquiry into this.
D-Air getting a ground only hitbox takes away specifically one combo, one that is actually highly impractical anyways
1. Now it instead has a combo where you can Bomb Throw > Footstool > D-Air Bounce 1 > D-Air Bounce 2 > F-Tilt
2, which deals surprisingly more damage and has a more desired effect (that and it can work more practically around higher damages thanks to how his D-Air works with AC).
This special hitbox, which is the "Body Jump" hitbox, is actually extremely better to link up to at higher damages (around 60%). Now previously, the hitbox would send opponents upward (which would result in them being too high for the second hit
3) and Link couldn't get a second hit when the opponent is on the ground
4. Now, Link can actually get both strikes on the opponent with an efficient 26% damage (or shield damage). If Link can AC before the opponent's shield comes loose
5, he can perform an F-Tilt or F-Smash and those will finish the job on that shield.
Now to your good.
Link's D-Smash 1 definitely has that power buff, and rightfully so for Link. All of Link's Smash attacks are fairly amazing in their own merit, but D-Smash 1 having an increase in power makes it quite usable more and more due to its fast hitboxes coming out (still, I recommend using Jab after SH N-Air
6 if the opponent shields). I won't comment about the F-Smash 2 buff though.
Skipping the whole UpB thing.
Let me add on to your F-Air thing. His Bomb > F-Air will actually kill earlier than Toon Link's on opponents now
7, and thanks to its massive power buff, Link can actually be able to pressure shields by a large amount. If the opponent is in quite the shield stun, Link could space it out so the opponent would get struck by the tip of his D-Smash or his entire F-Smash
8, which also results in a potential to absolute shield break. If Link can F-Air and strike with both hits, it deals 24% (or 25% in some cases) damage. That applies to shields. If he can do that and link up with D-Smash, it will potentially bust a shield (seeing as it might have been dealt 38% to 39% damage, and it takes what, 40% to bust one?) or absolutely bust a shield with F-Smash (both F-Air hits and an F-Smash will always deal enough damage to bust a shield, raw or stale).
Now yes, Link is definitely planted in mid-tier, but if people can manage to find ways to get the opponent's shield busted by Link's attacks, then Link could rise up into the upper mid-tier category, at least in the 23 to 27 spots
9. Link is a character who can pretty effectively punish his opponents now
10, and this is the character whom went every patch with buff after buff after buff done to him (except one nerf, but that's actually now just insignificant, really). Link may absolutely start seeing some action if people started doing more tournament representation with him
11. He has the extreme potential that is purely untapped by a lot of professionals, and if people can just put stuff behind them, they can find that Link has some high potential
12.
He does have a lot of more tolerable match ups now, especially on the lighter characters since he kills much earlier, and the fast fall or heavier characters just because he can actually get to them with an edge-guarding tool that is far more effective than previous patches.