Marth's combos/follow-ups would be sick. Marth doesn't have the aerial horizontal movement to chase with fairs if they DI away, but I can imagine him jumping towards them to get below them in the air at an angle for skill scoops and skill tilts.
Some limitations of Marth with 6 jumps you can take advantage of:
Marth's aerial's have a good window to punish between aerials: They're lagless when he lands, not between aerials in the air.
Marth doesn't have the horizontal movespeed of Falcon/puff to weave with this aerials and hide the cooldown of his aerials when he's poking... and besides nair (which you can't spam in the air anyway), they do not protect his body, so combined with the previous fact, he can't rush in. He'd be combo food if he just stayed in the air and thrusted (even if you space, fox and falcon can crouchcancel ****).
Because of his moveset and speed, I feel like 6jumpMarth would be very turtle, very annoying, but not necessarily 6 times as gay.
Falcon with laser? You've just bolstered his weakest point in approach with one of the best approaches in the game. Falco can laser-grab into a scrappy forward throw. Now you're giving Falcon laser->grab (his best move). The only sacrifice you make for a short hop laser is his full dash/dash dance...and my opinion is spacing a laser to gain the opposition is much more advantageous than dashdance camping or rolling a dice with an all out dash (you can still have those options after the laser anyway...)
Laser to save teammates, laser to put off-stage opponents into prime position for the dyick, laser the opponents as a continuation when they're at a hard angle to hit in the air, double laser from ledgehop->falcon k-k-k-moves, etc
A shortcoming Falcos have had is not being able to punish people when they jump over lasers, but Falcon is all over that with heavy heavy punishes.
Falcon now also has a B-move to turn around with mid-air. He can cross over people shielding with leaps, run off platforms with turnaround laser.
I think Laser Falcon fits the definition of **** better than 6jumpMarth, but who is more broken I dunno.