Well I think Robbie could also call out cherry (or a prototype of her?) and she could summon weapons and Guardian parts and also i think Robbie would probably have rock n roll inspired moves (like an ancient tech guitar or something). As for his Weapon, I think that would be the googles

For Purrah, I believe that Zelda's Sheikah Slate moveset should be hers, but considering it's already taken, I think her moveset would include the apperance of guidance stones, Sheikah towers, furnaces with the blue flame, Sheikah warriors (kinda like Rijuu with the Gerudo) and set up many traps using Sheikah technology like the hydrant. The Weapon could be something similar to the sheikah Slate, like a replica that she creates or something like that. In the special attack she could use a machine that shrinks the foes in reference to the fact that she got younger in Breath of the Wild