Well, that is why I don't my rare upgrade cards, unless I have 6 of them
But for the discussion, I agree with both parties, because:
Scaredgirl is afraid of one element becoming boycotted, and other over favoured
While Malduk is afraid of taking players choice, to make it fair.
There comes the Loyalist idea in play:
People who really want to fight for only some teams can tell that, but the masters have to decide if the will pick them, for a higher price.
People that don't mind, can be Mercenaries, but in that case, they will be able to be hired by ALL elements.
Because next war a lot of people will fight for the top-3 elements, hoping to be in a winning team, but the masters can only chose some of them, leaving the other loyalist UNHIRED.
That would add a new rule, you are either a Loyalist, or a Mercenary, you can't switch.
Otherwise all people will start as Loyalists, and become Mercenaries if their elements are filled, meaning favoured elements will have a first choice.
So:
Loyalist pickes 3 elements, but costs more to hire
Mercenary picks 12 elements, costs less
And when a (aspirant)player has chosen, he can't switch between them.
This way, people can either chose to fight the elements they want, with the risk of not being taken, of they can be free for all.
(the only thing you will have to do to make Loyalists more expensive, is to raise the starting limit, from 1 to 4).