As regards getting rid of Saddam, the US ended the Gulf War deliberately without toppling him because, we were told, to do so would leave a power vacuum which would be even more perilous. If that was true then, isn't it still true now?
As for the weapons of mass destruction, if the US now attacked Iraq, and if Iraq's current stockpiles of such weapons were hit, would that not create mass destruction within and perhaps beyond, Iraq? And if all the weapons were not destroyed, what would have been the point of the exercise?
Even if, almost miraculously, Iraq's weapons of mass destruction were all destroyed without immeasurable Iraqi and perhaps non-Iraqi casualties, and even if (no less miraculously) all the facilities for producing any more such weapons were also destroyed, what would prevent Saddam from reconstituting those facilities within a few years and then posing exactly the same perceived threat as now? At best, a military "solution" would seem to offer no more than quite a short respite. At its worst, it could have incalculably disastrous long-lasting effects.
The real problem is that there is no simple military solution, only least worst strategies. However, it is worth remembering that, on those occasions when Saddam has used biological or chemical weapons, he has done so in the knowledge that he could get away with it. It is remarkable that in the Gulf War, with his back to the wall, he did not make use of weapons of mass destruction. Presumably that was because he was sufficiently deterred by what he understood would be the consequences.
Perhaps the best the UN can do is to resolve absolutely and unanimously that any attack by Saddam on any other state will be met with an immediate and overwhelming response and to ensure that this deterrent is delivered.