I was thinking that if they buff marth, what way should he get buffed but still feel like "Marth"?
At first I was thinking, he could use a little more range (and I mean like a tiny bit, like the equivalent of the length of his tipper or so). But nah, that would cause a little more overlap with other swordsmen (shulk is the extreme range guy, ike is a longer range guy), etc. He still does have more range in general than non-swordsmen, though not by a lot.
Probably not power, because he's not really lacking that and I always thought of Marth more as a graceful, flowing type of character than a power type, even though he is slightly slower and more punish oriented than the speedies in each game.
In smash 4, it feels like his attacks, aerials especially, cover more area than in Brawl, and it looks quite beautiful. So even if his reach isn't much longer than non-sword characters, he still covers a big area with his attacks, which helps him be more flexible and follow up and weave in and out of things.
But I feel like, especially since he feels a bit weak right now, his ability to punish and follow up isn't that great. He can juggle a bit, do some reads, DB1 into FF nair into fsmash or something occasionally, but i feel like being punished by marth isn't that scary. Like, I really love seeing melee marth combos (sometimes seen in brawl but not to the extent in melee ofc), where you're juggling some guy repeatedly (less so the ones that are true combos, but the ones that need some reading) and then finish it off with a fsmash or something. I don't feel like marth can really do that at all in smash 4, only very rarely if you read very well.
So what if they just increased his hitstun a little?