The projectile absorption neutral B might be great for match ups with projectile characters, but it still doesn't deal with the rest of his match ups where he is easily outcamped.
Fixing his mobility would be a better buff in the long run. DK, Ike, and Charizard are great examples of heavy hitters (who can often hit just as hard as Ganon) with mobility that complements both their neutral and punish games. I think an inherent balance to being a heavy hitter is a weakness under pressure, so changes to Ganon to help him under pressure have to be really careful and slight tweaks (like a lower reaching grab, lower reaching jab, quicker spotdodge, etc).
PM is a game where tons of characters have very high mobility, and I don't think it cuts it anymore to have terrible mobility unless your moveset is godly, which Ganon's clearly isn't. Ike, DK, and Charizard are proof right now that having decently high mobility and being a heavy hitter will not break you (in this case, you'll be mid tier at best), so I think Ganon's mobility could be buffed to similar levels. I think we should actually discuss what kind of mobility buffs would be good for Ganon.
Ganon's moves are really effective at canceling out projectiles, the issue is that his mobility is so poor he struggles to put himself at an optimal position for that.
Altho, maybe you could take Ganon in a different direction than Ike, DK, and Charizard. Maybe instead of buffing his mobility, you could actually go ahead and make him really good under pressure. Ganon still can't approach people mainly due to his lack of mobility, and that's a terrible weakness to have. Maybe it'd balance out his ability to do well under pressure and make him a mid tier at best.