Well, Robo definitely needs a spot. Heal Beam is essentially the best healing move in the game, healing at about 10 health per magic point, so you should be healing your entire party for almost half their health by that point. Then Uzi Punch is just destruction, using Crisis Arm it deals somewhere around 5600 damage, eclipsing just about every other solo attack in the game in sheer damage. Shock, if I'm not mistaken, has the second highest magic multiplier, right behind Luminare, and though hampered by Robo's less then stellar magic stat, still does more magic damage then Flare. Lastly, once you get Armageddon Arm, use it with Dragon's Tear to crank out some serious damage. Just make sure you gave him some Speed Capsules, and a few Magic Capsules.
Crono of course makes it in, Luminare being the most powerful spell in the game and Frenzy doing some more then ample damage. That and he's the main the character, you couldn't go without him, could you?
Lastly, Ayla. Before I would have said Magus, but now, with Angel's Tiara and Regal Dress (both of which are found in DV) she finally manages to beat the glass ceiling created by Haste Helm. Her Triple Kick does some pretty insane damage, Valor Crest adds a little bit of damage output, and Charm still holds its usefulness. Plus, Beast Toss with Crisis Arm Robo does some of the highest damage in the game. Of course, if you get her to level 99, then she more or less becomes another Armageddon Arm Robo, with no Capsules required!
If you really feel like it, bring along Magus instead of Ayla, I did. While Dark Matter is pretty bad, his Magic stat will keep him above even Crono for a while, and his new weapon actualy makes him pretty decent physically. Also, no capsules. Plus, he looks damn cool.
