I talked about a similar thing a couple of days ago in chat. I think that having a "rainbow element" could have real potential. It would have powerful cards that use all elements. The cost number in the card would mean how many quanta it takes from all Elements. For example if the cost was 2, it would use 2 from each element, therefore a total cost of 24 quanta.
But like OldTrees said, the way Elements is coded, apparently makes this impossible, because the cost has to be from one element only.
If we wanted a new element, I think that Bloodshadow with his Void series, currently holds the 1st place.
1. We have Other cards. Having cards that cost a ridiculous amount typically means they are uber-powerful, and that's a no-no.
2. That idea is also not liked. Having 2 elements cost specifically for something is just... not bueno.
I disagree with both of these.
1. High cost cards are not automatically "uber-powerful". And if they are powerful, you can nerf them by upping the cost. Lets say I have a card that says "When you play thing card, you win the match". Pretty powerful, huh? Nope, because that card costs 1000 quanta to play. Of course we should NOT have cards like that, but the principle is the same: if you make powerful cards, you simply increase the cost, making the cards "slower".
2. "not liked"? I don't think we've had any polls on this subject, so you are only guessing. I don't see how someone would automatically
hate duo-cost cards. We basically already have them with cards that use an ability from a 2nd element. Why would people have a problem with cards costing two different types of quanta, but no problems with ability costing other type of quanta?
EDIT