For the weakness problem, there's always Rainbow Energy/Shadow Circle. Might as well do that because there's really not any other stadium that really helps the Cobalions and such. I'm really hoping they add something to make Metal a cool type to play again because I like all of the different kinds of effects that their attacks get. However, I'm not sure I would want to play Klinklang until Heavy Ball is reprinted or something like it.
There is the possibility that Metal could be like Grass type in Furious Fists. I mean, there are two new Metal EX cards that were revealed.