I think people covered the big problem: how to deal with promoting and demoting teams.
I do think that tanking is and should be a valid tactic. However, it should only be a tactic for grabbing draftees (especially since the draft is such a crap shoot, I've seen drafts with no 5 ball potential 18 year olds and others with 3 or 4). It shouldn't be a tactic for making a boatload of money. This has been addressed a bit; a team tanking out of the NBBA used to be able to net a few million dollars. Now they have a salary floor. If anything, I would like to see tanking teams take a hit in attendance for that season and the next season (which for the most part they do).
Sometimes you need to rebuild, and it makes sense to get a good young player to build around, but your fans should get really pissed off at you.