No thanks. I'm not a big proponent of the, "If a little is good, more must be better!" way of thinking. Besides, adding another round would basically be recreating the NBA playoffs as March Madness and I, for one, don't want that.
Your other suggestions seem to carry the tinge of, "Well, I don't care about the IST, but I do care about the playoffs, so make the IST count for the playoffs, and then I'll care about it." I say let the IST be its own thing; it shouldn't have s**t to do with the standings or the playoffs.