Well Toaster did say that Ness' Pk thunder traveled faster, but that Lucas took more time to fall. after the move. Maybe letting Ness take more time to fall after PK thunder could make it easier to recover with him. I'm thinking about positioning here.
About the magnet... I don't know what to do with it. Offense up was a good way to differentiate the two for Lucas., so giving him defense up might be a problem. I mean, what's it going to do? Give him a temporary Super armour? Unlike Offense up, I don't think that can be very useful. It doesn't help comboes either.
He doesn't have a lot of moves to pick from that would make sense. Maybe he could use his psy powers to get an extended grab?
Another possibility is a Psy-up. Make his next few B moves more potent? Like he could store charges (Shorter than Lucas' individually) and then use them. Like PK Fire would crease a large fire pillar, stunning more, causing more damage. PK Thunder would be large, damaging and provide better recovery. The Magnet would cause electric damage. The PK flash would have a larger explosive force. I can see problems with my suggestion, and I don,t think it should be implemented as I brought it here, but I'm throwing it in anyways.
Edit: Oh and PK flash could be "Charged" on Ness, allowing him to go "gtfo" on the enemy if he stands too close. Of course, it might be like a charged, weaker rest with a little more range. The punishment for a failed discharge would be being an easy target for a second or two.