Well,
if we consider that they were able to choose any character in the chess game, I think chosen the king would have be weird :
if you play chess, you know that the king almost doesn't make anything.
He's here only to be protected : so choosing to be him would mean that you do not want to be involved in the battle, and we all know Ron, he's not that kind of person.
Therefore, the description of each player regarding the figures they are representing is very well done in the first post of this topic.
Now as you said, even if Ron has to sacrifice himself to help Harry winning, he doesn't die, and furthermore as said before he's the only one to be on an horse : so if this chess game shows us the future, we can easily imagine that Ron will have to sacrifice a part of him to help harry in his battle versus VD, but that he won't die.
Concerning the other character, such as Mc Gonagall, well we all know that in any battle, people sometimes die in order to reach your goal. Too bad for the professor, but we know now that JKR won't hesitate to kill someone if she had planned to do so.
and by the way, excellent theory.
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