If what Saddam might do with WMDs...

Is a 'good enough' reason to remove him from power, does the lack of WMDs change things?

Answer: no. We know what Saddam did when he had WMDs...

Here's James Zumwalt in "Marine Corps Times" on the subject:
"Obeidi’s revelations raise an interesting question: If Saddam acted as if he had WMDs because he believed, however illogically, he possessed them, how can we fault our own intelligence agencies and the president from arriving at a similar conclusion? After all, if it walks like a duck and quacks like a duck, one would not be unreasonable in concluding it was a duck — even if such a conclusion later turned out to be inaccurate."
Read it all.