I kinda like the idea of an anti-projectile character. Like what has already been said, Pit's a good example of one. Lots of reflectors... and I totally love how Wings of Icarus can cancel out a lot of projectiles. And wingdashing provides so much utility... I'm gonna cry if it doesn't return. Seriously, wingdashing is one of my fave techniques in Brawl. :/
Similar to PSI Magnet, a move could absorb projectiles, and once absorbed, some sort of effect happens. Chrom could be powered up in some way, maybe buffing his defence or offence... or something cuz I'm kinda bad when coming up with ideas like this. No joke. But anything so it will be different than PSI Magnet.
Having a move that could absorb and "store" projectiles is another idea. Maybe the move could be released at any time, and the more moves it adsorbed, the stronger the damage (having a cap of how many attacks it can store). Perhaps if Chrom is a stance-user, the released power would have a different added effect depending in the current stance.
In many fighting games, characters have teleports, multi-hit attacks, and other moves that can cancel and punish projectiles. Not really sure how teleporting would work in Smash though... but yeah, using some standard moves could be an easier way of canceling projectiles.
Evasion is another idea. Perhaps Chrom could have a charge/dash move, that allows him to pass throw projectiles, attacking opponents if in contact. Or some sort of special roll move... Anything that would make him a good fighter to punish projectile users.
