On The Current Topic: I'd say Fire/Rock, as it's too easily breakable. Plus it would be sorta slow. They should give a good Defense to ALL Fire/Rock Types they ever introduce (I know Magcargo, but I'm referring to anything they introduce) and a good attack at the same time. They also need to give a helpful speed if they are as strong/stronger than Starters. Then, give them a wide moveset. Then, it'll become a GREAT Type Combination, although it's got a large amount of weaknesses (Ground, Fighting, Rock and Water which are all used commonly) and an even larger amount of neutrals (Grass, Dragon, Ghost, Steel, Dark, Electric and Psychic) which makes it quite a vulnerable Combo.