Huh maybe, ya. Maybe Godzilla could get like a metal mouth thing that covers his teeth.

Kong: Either an Upgraded Beast Glove, Battle Axe, or a Battle Armour with Both...

Godzilla: a Complete Evolved Form since Evolved Godzilla's designer pretty much implied that the Evolved Godzilla we see in GxK is a halfway/midway transformation... So a 100% complete Evolved Godzilla is expected to happen for Goji's upgrade...

Shimo: Some form of power augmenting battle armour, or an energy boost...