I didn't read all 7 pages, so I apologize if these things have been covered already.
Most ff leagues are created to mimic the NFL. But, it's not the end all, be all, to say that the NFL does or doesn't do it, so why should fantasy leagues. 2 QB leagues are a good example of this. What it does require is a set of rules that all owners agree to before the start of the season. There is no right or wrong answer, unless a rule is broken.
I don't like tanking, I prefer to play to win every game and let the chips fall where they may. I wouldn't play in a league that had no rules to address it. However, those that complain one teams tanking could keep another team out of the playoffs are forgetting, if the team wins he may be keeping a different team from making the playoffs as well. Every action has an equal and opposite reaction.
We are in discussion about rule changes to address tanking. Currently, we have rules against starting players on Bye weeks, IR, or players that are listed as out for multiple weeks. Owners still find ways to tank in our league for better draft position.