Of course, one proposal doesn't necessarily deny the other, in theory.
But, I tried to watch the whole ensemble taking into consideration both the 'need' of new improvements for the war chariots and of a new conceptual hero; as if the two proposals were intertwined with each other.
So, I believe that a new chariot hero combined with new improvements for the chariots themselves could end up being an 'excessive' focus on that
chariot theme I referred to previously, thus preventing us from having another new innovative concept for a hero beside chariots; while, the previous two proposals might really bring to the faction of the Iron Hills two different new aspects, each belonging to different fields, and resulting in a more evident diversity.
I see your idea as something in between (focus on chariots and the need of a hero), which doesn't completely convince me.
I don't really have anything in particular against it; it's just that I'm not 100% sure about it for the exposed reasons.
Not to mention that I think that the previous two proposals are already justly balanced and well-conceived due to the considerable efforts poured into them (achieved by a constant work on polishing them).
Obviously, as you wrote, everything will be up to the Edain Team's will.
And, it's not so implausible that we may be likely to find a reasonable
compromise (often unexpected) between two or more sides during the natural development and continuation of the debate.
This is what usually and rightly happens here, leading many times to greater outcomes than the ones initially planned