1) Scrap the Breda variant that sent the best French army and the best French light armored division (1st DLM) all the way across Belgium into Holland instead of holding it in central reserve. That cut French reserves in half and the what was left was much less mobile.
2) Keep the third French heavy armored division (DCR) in reserve instead of pretending it was ready to fight. It wasn't, and it's failure in the early fighting destroyed it. It could have been very useful later on.
3) Prevent commanders in central Belgium from grabbing control of the Somua S35s of the 3rd DLM and using them in penny packets on defense. The 3rd DLM was supposed to screen the infantry until they got set up, then withdraw and be available as a reserve. It took days the French didn't have to pry those tanks out of the hands of the front-line commanders.
4) The French needed to understand that Belgium did not plan to fight in the Ardennes. Belgium just blew bridges and withdrew for the most part, which was a major reason--though not the only one--the Germans crossed the Ardennes in three days rather than the ten days the French were counting on. If the French understood that Belgium was going to withdraw without a fight, they would also understand that going as deep into Belgium as they did historically was inviting disaster because the Belgian withdrawal left a very weak flank wide open.
5) Have bad weather delay the German invasion by about a week to ten days. That might give the French time to resolve their command situation. Reynaud (French Premier) wanted Gamelin (French commander) sacked because he seemed more interested in making sure he didn't get blamed for any fiascoes than in prevent them. Technically, the French government had fallen over the issue at the moment the Germans attacked. Gamelin was a smart man, but had been doing politics too long and had gotten infected with a politician's style of leadership without accountability.
I'm not sure the French would hold given all of that, but they would have a better shot at it.