To tank properly you need sharp minds with a vision in charge, real football people with a clear, structured plan. In other words, forget about it.
Also, the Cowboys have one of the dumbest, most short-sighted fan bases in all sports. Some of us understand the value and necessity of a rebuild in modern sports but the homers just want something to cheer for. They don't care about long-term success, they want their instant gratification and meaningless regular season wins/early playoff exits. They enable the cycle of perpetual mediocrity and they're too dense to realize it.