I've heard of this 'plan'. Apparently it emerged in response to a wargame requirement Halder issued in November 1939. He wanted to test three alternative ideas for Case yellow. The first had the German main effort north of the Meuse river, the second placed the main effort south of the Meuse - in the Ardennes, and the third had no main effort, but with the attack evenly weighted across the front.
There are claims the second option showed more promise when tested at the Zossen map exercises in early December. The CoS of Army Group A, a general named Manstein claimed the Ardennes option was the best, and expanded on the Zossen war game manuver writing portions of a detailed plan for Army Group A to use were that option choosen. I've been unable to find any original documents of that planing and suspect it was all discarded when Manstein got his promotion to corps command in January 1940. Apparently he mentioned it to Hilter because after Hitler had his routine meeting with several newly promoted corps commanders in January he asked Halder about it.
Halder refered to his report on the December war game, which Hitler had already seen. In it Halder and other officers present judged either weighted attack to show some promise, but neither producing decisive results. They all agreed the third option, with the mass of manuver evenly spread out was the least sucessful on the map.
The Melchin incident caused Hitler to cancel the scheduled January offensive, and Halder took the opportunity to completely rework the plan in place, which was to weight the offensive north of the Meuse river. Over the next three months his staff and the army group commanders completely rebuilt the plan and refined it extensively.
I dont think we need to go into the details here, there are dozens of descriptions of the may offensive and 800,000 dead and maimed of that summer.
What is really intersting is a reamrk made by Guderian in a very rare and obscure book he published post war. As tank or armored warfare fans know Gunderian was one of the principles in creating the German mechanized forces in the 1930s. He commanded one of the armored corps in the May-August battle. This book, titled 'Panzer Leader' had a limited print run and AFIK has never been translated to English. In it Guderian makes the argument the flaw of the May offensive was the dispersal of the armored corps among the several armys. One in the Netherlands, two on the Belgian plains, one south of the Meuse River in the Ardennes, and one initially in reserve, as part of the Swiss deception gambit. Guderian argues at least four of these corps should have been massed in a single "Panzer Army" that would charge across the Masstrict province, by pass Liege, and straight on between Namur and Brussels. Once in the vicinity of Mons/Lille this 'Panzer Army' could either move on to the Channel and split the Allied armies, or turn south and threaten Paris.
I tested this idea on the game board and it has some merit. If the Allied player does not see it coming his own reserves will be out of position and the Allied front can certainly be badly disrupted. Under the right circumstance the German pieces might even reach the Channel, or Paris, but I would not count on it. the Allied player would have to make a lot of mistakes. Tho given the number of mistakes made in the actual campaign this might occur. Suprisingly the massing of the German mechanized corps did not create traffic jams on the game board. Tho one would expect them in the converging roads around Masstrict and the limited bridges across the Meuse River and Albert Canal
Guderian had nothing to say about placing such a armored army in the Ardennes, Halders war game with the Schwerpunkt in the Ardennes, or Mansteins elaboration on that. I would note that one German 'panzer korps' did operate in the Ardennes with little trouble. More important is that all the Belgian regiments deployed there were motorized, and the French sent a substantial light mechanized force into the Ardennes as a forward screen.