To get the White Glint AC parts, you have to do the mission "DEFEND Line Ark." In the mission, White Glint is your ally and will disable one of your enemy AC's, shortly before being disabled by the other AC. You will then go 1-on-1 with Fragile (if you have beat him in the arena already, use the same tactic when you beat him, except in a fairly small area). After you kill Fragile, and after the debriefing, you should get the White Glint AC parts.
To get the huge cannon that Rai-Den has, you have to do the mission: "Great Wall" on hard difficulty. In the mission, when you get near to the front of the Great Wall in the inside, Great Wall will split and Rai-Den will be in the entrance shooting at you. Just kill him with dual grenade launchers and kill the Great Wall and you should acquire his cannon.
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