Looking at ganon's current problems and play style, a change to suit him more towards what his charater is strong at as well as his theme as a warlock would help him in both viability and the fun department.
I'd love to see Ganaondorf not only become more viable, but separate from his previous clone... captain falcon. As a bait and punish zone controlling character but incredibly slow ganon would work great as an odd ball slow zoner, sort of like the super heavy, slow version of samus in a sort. Giving ganon even a mediocre projectile would really allow ganon to excel in his defensive play style and make up for his abysmal run/chasing speed, with already poor recovery and poor frame data, he could use anything he can get, especially a spacing tool. Seeing as Ganon is not only a warlock, a magical character and shown to have projectiles in the Zelda games (in ocarina of time he even floats in place and shoots light orbs are you). Also to help his recovery and keep with the character theme, a peach like double jump float would help ganon more than you could ever imagine for recovery.
I'd suggest removing his current side smash, replace his current side smash with his warlock punch which you would now charge for the full current effect, this would thus give ganon space for a new neutral B. His side smash would gain armor properties just as his warlock punch does on start up. This also gives him a similar attack to falcon with the punch attack but instead this is now his smash and not a shared neutral B with falcon. Additional differences this would make it generally faster to apply on ground as you don't need to fully charge the warlock punch for a quicker less power full smash version and not allow ganon to warlock punch while in the air since it is a smash attack. The satisfaction of landing a warlock punch is awesome, making it non charge smash come out a little quicker for less power would just be satisfying to land on people.
With the neutral B slot free as his new side smash, his new Neutral B would be a chargeable light orb projectile. Distinctly different form other charge projectiles acting as a cross between megaman's metal blade in launch properties and bowser jr.'s cannon ball in speed and general projectile properties. The light orb from ocarina of time would be the change and a charge projectile, you can either charge the full shot and release or like other charge attacks, quickly double tab B to release a still slow uncharged version. During the start up launch frames of the orb you can in put a basic direction like megaman's metal blade and launch the slow moving orb in the chosen direction (default non-directional input is forward facing launch). This projectile travels roughly the same speed as the cannon ball, has high priority over most other projectiles, has a piercing property to it like the cannon ball, is considered an energy projectile allowing ness to absorb it, not dissipate until a set long distance and of course be reflected. The projectile has hefty damage on hit but relatively low knock back, equivalent to taking lightning jab making this a damage option for ganon, but not a kill move. The start up and end lag of the move would be significant but faster than the current version of cannon ball, so slow but safe at distance. This would also be the only instance of a charge hold projectile that can be angle changed and the only non killing charge hold projectile as damage is the main focus. Double tapping B, then immediately pressing a direction upon the start up of the light ball just like metal blade (but requires double tap b) is a unique mechanic and would require getting used to.
The float on the 2nd jump would be nice to give him a heavy peach feel and lore wise matches the characters abilities, while also only partially increasing his horizontal recovery from gimping once (you only get 1 jump before recovering to the edge). He'l still have bad recovery as he has little vertical recovery and hitting him out of float essentially dooms him, but at least his much needed buffed abysmal recovery would be improved without making him too good at recovery.
The rest of his kit is solid and fits his defensive punish theme, but now he has some control over the stage being able to float briefly in the air (also allowing him to have an option to deal with heavy projectiles) and have a mediocre but still available projectile to force an approach. Being both gigantic, poor crouch, slow in terms of dash speed and frame data really gives him a good reason to have odd tools to deal with heavy projectiles and people that run from him without just shield or dash attack. Also how awesome would it be seeing defensive ganon zoning, while most zoners are very fast and mobile, ganon doesn't care he holds his ground and tanks enemy approaches.
TLDR VERSION: VVVV
-Remove current side smash, Replace it with his current Neutral B warlock punch, full charge of side smash = about current warlock punch, uncharged is a less powerful version. Retains similar properties (armor during move).
-New Neutral B: Give him a slow moving projectile (Bowser Jr. Cannonball like) that he charges and aims like megaman's metal blade in multi directions. Has high damage and a decent hit stun but low knock back so it's not a KO move. Slow move in terms of start up and recovery.
-Make double Jump hold to float similar to peach but for less time. He's a warlock, he can float in ocarina of time why not here when it matters. Helps with projectile dodging and recovery while still keeping him with bad recovery (even if slightly improved).
-Keep the rest of his kit the way it is, he can even (and should) keep his bad frame data, size and run speed to balance his new abilities.