The Belgians and to a lesser extent the Dutch not waiting until the 11th hour forcing all those powerful mobile units to make a dash for the DyleThis site does propose essentially this, albeit only in French and it also tackles other subjects like pre-WW1 French military or some WW2 Wallied PODs.
There were plenty of options for France to perform better in WW2, better positionning before the Battle and better reactions during the Battle being rather "easy" because they don't require money or excessive time but just being somewhat smart. The vulnerability of the Ardennes was understood both by some officers as early as 1937-38 and later on by French intel services just before the attack so this could have been addressed with some preparations and better training and alert by troops here. The Breda part of the French plan was the least liked and pretty much only Gamelin supported it so it could have been scrapped, saving the best French Army to be used in reserve, ideally near the Ardennes where it originally was.
Trusting the radio a bit more and being less indecisive in general would have allowed the French to react more quickly and maybe get enough forces in the path of the Sickle to eventually stop it before things became too bad.
RE procurement and industrial build up, there were several opportunities to choose better designs and get advice/equipment from French or foreign engineers and industrials in the US and UK, which would have allowed for faster and better manufacturing methods and better fuel production and refinement methods to be used (the latter was relevant as France didn't have access to enough of the decent quality fuels the British and Americans had access later on, which limited engine performance and prevented the use of some of the better engines. This is a relatively straightforward way to get improvements without having insanely advanced engine tech). France itself had some decent base in some areas for proper radio comms and even a modest radar network.
Had they opted to join the Allies earlier then the Allies would not have to have rushed the job and probably have had some of the more mobile units in reserve.
Basically I am blaming the Belgians for the whole mess LOL