Is there a consensus among Steem witnesses as to if they would go the ethereum classic route or the current edited ethereum route?

It is up to individual witnesses to express their views on these types of things. I am not really in a position to speak for the "group".

Is there any instance of a huge wallet being compromised or updated historically?

There is a long while back. If you search through historical information on past hardforks, you will probably find it.