"If there is a "potential" for WMD (and none discovered), it means Iraq was no immediate threat to the world. "
If Saddam was taking steps to get ready to restart WMD, he was violating cease fire agreement.

"Which is why there were UN inspectors before the war."
The inspectors had been forced out of Iraq, they returned because Saddam was miltarily threaten by Coalition invasion forces at his border.

"To become a real threat, it would have involved so many scientists and technicians and money that it would have easily been spotted."

To have several divisions of armored troops ready to attack Iraq over a long duration of time, is expensive and politically unwise. Saddam required a threat before he would allow inspectors in Iraq.
Didn't everyone want sanctions lifted? Didn't everyone want the "No Fly Zone" to end? Didn't everyone want the war with Iraq to end?
Was it the American govt [Bush, Clinton, through to Bush] that was preventing this war from ending? Or was it Saddam who was preventing this war from ending. Didn't Saddam sign an agreement which provided a means to end the conflict? Didn't Saddam violate this agreement?
At the Moment we have Iraq forming a new govt. There is no good reasons for continuing the "No fly Zone" or having sanctions. If it wasn't for a small group under the banner of Saddam and misc terrorists, Iraq would be at peace. So Saddam is still trying to continue the war, but he no longer controls the Iraq people. The ACTUAL real threat is leaders who control govts who want war instead of wanting peace. Does the French govt want war or do they want peace? The US govt is giving over 20 billion dollars to Iraq get to the point of having Iraq no longer at war. How much money does France want to give? Or instead of giving what is the least that France will accept that Iraq has to pay back on the loans it previously made with the Saddam regime?