Zelda isn't even true to her game. Both her and Ganondorf are supposed to have swords and some really cool moves. Not as bad as Captain Gandondorf but like it has been said, she IS Sheik. ZELDA was trained by a Sheikah.
She is actually true to her game. Zelda never had a weapon until Wind Waker and that's with a bow which would have been pretty damn interesting to see a magical archer like that. I mean, we already have a Legolas-like fighter with the Pits. After that, she had a plot-only rapier that was only used in combat when she was puppeteered by Ganondorf and then she had a harp in Skyward Sword which was used by, you guessed it! Sheik in Hyrule Warriors. Hyrule Warriors expanded on the idea that Zelda was competent with a rapier, could use a baton like a magical wand, and later added rods which also are mage-y. If we archetyped Link, Ganondorf, and Zelda, Link would be the thief, the guile hero who uses items, exploits weak points, and would prefer to not use brute force to win; Ganondorf would be the fighter or magic knight who overwhelms his opponents, endures hits, and if capable like Cecil Harvey, some rudimentary magic which in Ganondorf's case, is more like Cecil's Dark Knight magic where it's just pure offense; and finally, Zelda's the mage.
I won't go into Ganondorf since you can debate whether or not he's supposed to be a warlock like in pre-Wind Waker where he mostly used magic and sometimes weapons if you got too close or a spellsword post-Wind Waker where he used weapons and magic. In Smash's case? He leans more towards a warlock. Yes, a warlock, but more of an Eastern or Wuxia one where his magic is infused with his martial arts. Do people like that? Debatable. Would people prefer Ganondorf as a spellsword? Debatable, but it leans towards yes more than evil, kung fu sage, master of the Purple Flames Fist Ganondorf.
Bigger hitboxes on magic-based moves. These things should be difficult to avoid if caught in the wrong situation. For example, Zelda's forward tilt is actually friggin' powerful, and kills pretty damn early for a forward tilt. However, it has no range. If it could work like Ganondorf's own f-tilt, as a kill move that the opponent has to be extremely wary of at high percents, it would serve more of a purpose.
It's not the range that's a problem; it's the speed. Ike and Zelda's Ftilt are almost the same in hit speed; Ike's is frame 13 while Zelda's is 12. Both have the same active frames of 2. Difference besides range? Ike's always does a consistent 12.5%, 30 base, and 97 growth while Zelda's has sour-spots that do 10%, a sweet-spot that does 12%, and all hitboxes do 50 base, and 88 growth. Both Ftilts launch at an angle of 361, both are disjointed with Zelda's being transcendent, and both will kill at similar percents, but which do you think is safer? Ike's massive sword or Zelda's dinky little arm? Zelda's Ftilt could be given an Ike Ftilt treatment where it no longer has sweet-spots and sour-spots, but is faster - I think Ike's used to be frame 14? - and more consistent. So, Zelda's Ftilt could be frame 10 or 11 and only does 11(.5)%. Right now, it's an okay move that does work as a strong spacing move, but Zelda could always jab instead and suffer much less recovery frames, jab is frame 11 and takes 8 frame to recover to Ftilt's 26 which is pretty normal for a tilt - 1 less than Ganondorf's Ftilt.
Less recovery on Smash Attacks and perhaps other moves. Basically give her some more Meta Knight F-smash type attacks. This doesn't mean that she's a speedster now, but it gives her stuff to throw out in neutral without being too scared of retaliation.
Note: my recovery spreadsheet is off by a frame or so for all characters... I think, so it'll need to be fixed. Still, it's around the ballpark, so...
Her Smashes have average recovery... Jab, Utilt, and Dtilt on the other hand have fast recovery at 8, 11, and 13 respectively. There's a reason why Zelda players just jab in place or move and jab. It's also why she can jab to jab. That being said, Zelda with say, 17 frames - same as Meta Knight's Side Smash - as opposed to 25 frames wouldn't do much harm... Zelda players already Side Smash bait because of the 5 active frames its out and because it's transcendent. Yeah, a lot of Zelda's moves are transcendent. From her frame data thread, jab, dash attack, Utilt, Ftilt, Up Smash - last hit is not for some reason -, Side Smash, Nair, Uair, and the sweet-spot of Fair, Bair, and Dair are all transcendent.
Now, her landing lag on the other hand is... really bad. The lowest is 18 on Dair - used to be 21. Highest? 25 on Fair followed by 23 on Bair and 19 on Nair and Uair - used to be 22 for Uair. Granted, Nair has a good auto-cancel window of before 4 and after 38 which is better than Falco's Nair which was stolen from Zelda and Zelda never got any compensation like... 14 frames of landing lag instead of 19. Oh, wait, 1.0.8 changed her landing lag of Nair from 22 to 19... Why was it 22? Nair is good, but it's not some kind of magical, broken kill move of doom that ironically, Sheik doesn't care about when she's got slaps. Her Dair also has a good auto-cancel window of before 4 and after 40. Everything else? Uair before 5 and after 55, Fair before 4 and after 50, and Bair before 3 and after 52. Uair is the only one I don't get since Fair and Bair would be ridiculous if they had some semblance of a good auto-cancel. It's funny since Ike swinging his sword like a helicopter takes 4 less landing frames and has a better after auto-cancel of before 51. Ike doesn't use Uair close to the ground and neither does Zelda, but Ike's get a better "cushion" in case he does and he can when it has better horizontal range. Zelda? Nooooope.
Zelda's hop is 41 frames and jump is 62 frames. Like most characters, most or all of her aerials can auto-cancel from a jump. From a hop. Only Nair and Dair can, but you need to be frame perfect with Dair. Let's go back to Ike because of his Uair comparison thing and not because he's anything similar to her; Ike's hop is 37 frames and jump is 52 frames. Going off of that, Ike can auto-cancel all of his aerials except for Nair? Weird... It's got an after of 64, but whatever, 14 landing frames. From a hop? Fair and Bair. Fair and Bair are among Ike's greatest tools and setting up Fair from an U-throw or a D-throw? Ike doesn't need to auto-cancel it! But it's the safety of it all and let's say Ike fails to auto-cancel it; Ike will take 18 frames of landing lag and if he hits, a consistent 12%. With Bair he'll take 19 frames of landing lag and deal 14%. Zelda? If Zelda manages to hit with Fair or Bair, she better hopes she sweet-spots to do 20% and be somewhat of a threat on-shield or only do 4% and lay their questioning her life. 23 to 25 frames of landing lag is one dead Zelda. Needing to sweet-spot it is even worse when Ike can just Bair anywhere and still launch you. Falco's even more notorious where being behind him for no reason at all means a frame 4, 13%, 130 growth Bair will kill. And all Falco needs to do is input a Bair. Zelda needs to input a Bair and drift out enough so her foot hits and everyone knows - Hi, Sheik - that Zelda's got long limbs.
Sour-spotting her Fair and Bair isn't like sour-spotting Marth, Roy, or even Samus's Fair (excludes Sammy) and Bair (includes Sammy). Their sour-spots are strong enough where they're hitting you out and not doinig a weird leg slap that will only incentivize you to slap Zelda back. It's safety, versatile, and even range that Zelda lacks. Her Nair, Uair, and Dair are good moves, but they're not enough when you try to do something in the air. Nair isn't a horizontal move; it's a central move. Uair and Dair are vertical moves and unless you're Cloud or even Falco and Ryu who either have a giant disjoint or a more angled hitbox, you're not going to be able use Dair to poke or approach. Fair and Bair both being sweet-spot moves with extremely weak, short-living sour-spots makes it much worse when she doesn't really have a horizontal aerial tool to work with. Can she land them? Yeah, but it's going to be hella difficult when people know that's all she has and if she fails them, it's not like Marth and Roy who can still wall you out and don't have 1 active frame to work with for their sweet-spots. Captain Falcon's Fair which also has 1 active frame sweet-spot has a sour-spot that stays out for 16 frames to Zelda's 4 for Fair and 3 for Bair. If it weren't for the small hitbox and high startup of 14, Captain Falcon's Fair could actually be used like a sex kick. The high landing lag doesn't help either. Worse case scenario for Marth and Roy is Marth's going to take 17 frames from Bair or 16 from Fair if he fails to auto-cancel them which is kind of stupid when he 4 frames of leeway to auto-cancel Bair from a hop and is Roy's going to take 19 frames with Bair or 15 with Fair if he decides to use them over Nair which takes 13. Roy can't auto-cancel any of his aerial from a hop apparently, they're over by 2 at the lowest, but he can auto-cancel everything but Dair - this move... - from a jump and Roy's a low jumper and fast faller, so... yeah... Even then, who's got the better landing lag and auto-cancel windows? Definitely not Zelda. Who's got the more versatile aerials? If you answered Sheik aka Fake Zelda, then you're correct!
Stronger kill throw(s). If psychics can have cool kill throws, why not a magician? I do believe one of her throws (back? forward?) is decently potent, but if she had a scarier one it could work well with the fact that opponents are encouraged to shield against her due to Up B. The threat of the death throw then instead sets up for elevator kills.
Yeah, her B-throw kills, but relative to other B-throw kills, it's not that strong? U-throw should definitely kill or be a setup throw. Right now, I think it's kind of both, but not leaning towards either which makes it not work as well... That and since she doesn't have a stupid disjointed laser like Falco's, means she has to have one or the other. F-throw killing would be great... Now, F-throw being able to setup Fair or Bair? Even better.