After Kahi's post, I don't know if I should post my thoughts here or start my own topic... I'll post here, I guess, since it seems like this is where most of the discussion is happening
Man, this thread gives me huge throwbacks to when I would lurk and post on the Elements Forum on BZP~
Anyway, to just throw in my two cents here (and fair warning, some of them are unpopular opinions): If G3 does keep the same cast of the Toa Mata, I would be fine if Pohatu's element was changed to Iron. I know it's already been discussed at length here before, but if one of the limiting reasons to Pohatu using it as his element is because there's no pure iron in the environment and what is there is brittle iron ore, he could create some himself. It seems like the whole thing about Toa being able to create their elements as well as control it was forgotten at times here? In addition, Iron encompasses all metals, not just the namesake one ^^;
Otherwise, I think I'd prefer a new cast of characters especially if the main elements list and/or the powers under each element change. Major unpopular opinion, I'd kind of like to see a cast of eight Toa but that's a whole can of beans for another topic
On the actual topic of elements though. So, my approach has always been a mythological or comic-book-esque approach to elements and elemental powers rather than a science based one. That said, I'd be fine with Earth and Stone merging into one element since they both deal with... well... the earth and ground-based substances.
I think Water and Ice should be kept separate. Putting aside the H2O thing, I feel like the connotations and power sets are distinct from one another. The element of Ice creates and controls snow and ice; their users are tolerant of extremely low temperatures (on that note, are the sub-powers for each element being retained? Like Earth has night-vision and sensitivity to vibrations, Water is more agile underwater, etc?). Whereas the element of Water creates and controls water. Taken especially with the tropical setting, I picture a sea-faring folk with values in sociality and community which would be pretty different from say a more reclusive high-mountain ice village.
Last aside, there was talk about Heat as an element because of the Water/Ice debate. But Toa of Fire can create and control heat too in addition to their control over flames. Remember when Vakama absorbed all the heat in a room when confronting that fire elemental? Or when Lhikan located the Nui Stone in Tuyet's home by sensing its heat? Just a friendly reminder ^^;
I liked Psionics as an element in G1, personally. Thought of it as an element of the mind or consciousness. As far as elements being forces of nature, the mind can be a pretty powerful one. I also just liked it because it opened the potential for a Jean Grey type of character/power set
Edited for Double Post - Waj