Hi Drett,
I get where you're coming from because I've seen Mormons using that argument but...
Do you think only bishops should be blameless, temperate, sober-minded, of good behavior, and hospitable? Of course an elder has more responsibility because he has a position of influence, but shouldn't all Christians strive to be as godly as possible? Why is it that the elder has to be a man of only one wife? Maybe because it is the ideal situation, especially for an elder? In that case, all Christians should follow the example, shouldn't we?
Also to say that just that part of 1 Corinthians was ONLY directed to that church at that age would be the same as saying that none of the letters apply to us right now. Very dangerous. Of course we should consider the context, but the command is not only for that time. The Philippians apparently had a habit of getting discouraged from doing good when Paul was away (2:12) but that doesn't mean we are not to follow the commands he gave them just because we are not the Philippians.
Augustine was a great teacher but he was not inerrant.''The two shall become one flesh'' from the beginning, later quoted by Jesus himself, remains as the command. Not to mention that the analogy between Husband and Wife and Christ and the Church wouldn't make sense if a man married many women. As far as I know, Jesus only has one Church.