IMHO, there shouldn't be a Wind type. Why not just group everything airborne and air-related under one type? The reason why there's a Flying type is because Pokemon are like animals and so those with the Flying type usually have wings or are in mid-air. I also feel that Crystal type would be redundant. It just an expansion from Rock types with a few tweaks so I don't see any reason to actually include it.
I've always thought that Steel types should be weak to poison, given that acids can corrode metals. It'd also make the poison type useful offensively.
Makes total sense. And how about throwing in Water since it rusts metals? (Then there may be another ability like Heatproof but for Water, like Rustproof) :P
I also like the idea of Earth types, it makes it less confusing between Rock and Ground. Well, I can understand that Rock types are weak to Ground types in the scenario that pebbles and stones would rattle and break when there's an earthquake but considering that boulders and rocks originate from the earth, I think it would clear up a few misunderstandings about these two types. I rather memorise "Ice is SE to Earth" than "Ice is SE to Ground but weak to Rock". Catch my drift? X3
I would appreciate the coming of Light types, it would be like a better improved version of Psychic with a mix of Fire and Electric. And since we already have Dark, there should be a suitable polar opposite. And I feel that Dark should just remove its immunity, not everyone is afraid of the dark, ya know. Take me for instance. xD
And throwing in my 2 cents, I should suggest that Dragon be given more weaknesses than just Ice and itself. I understand well that it resists the four element types (Fire, Grass, Electric and Water). I don't know if it's plausible but as I've said, it's just my opinion so don't shoot me. xP
I think that those who defend the type chart as-is are just traditionalists. It is a better chart and more complete than any other game I've ever seen, but it's not balanced--far from it. Just look at Grass, Water, and Fire. The types are not equally balanced by any means. Also, right now, the only way to do parallel pokemon (like Reshiram and Zekrom, Electivire and Magmortar, etc...) is Fire and Electric. Even then, Electric has huge advantages over fire. Also, types like Poison, Bug, and Flying are underused and not quite balanced. (Flying because there is only one pure flying type.)
Although I somewhat more or less concur with you, I've to say you could have put it more politely. Sometimes people have their own reasons so you can't blame them for being traditional or archaic. Sometimes simplicity is always the best method. Anyways, moving along from this awkward sidetrack of human psychology....
I don't think Bug types can be deemed as underused. Look at Scizor, Yanmega, Escavalier, Volcarona etc! They are all getting more and more popular for their goodness! :) Also, I don't get why Psychic is effective on Poison. Lol, I have lots of questions. x3