So, I finally managed to hold out as France (3rd attempt)
I went for initial CIC build-up until I had almost three full building lines. And MIC from then on. I also used all industrial foci to increase production. Other constructions were 3x8 forts in between end of Maginot and place where Meuse turns north, into Belgium, 4 additional forts in Alps, one in each of the endangered provinces, and 2 AA there. During the war I added radar sites along both fronts. After the war started I converted 4-5 CIC to MIC, but as trade with other Allies ramped up I was able to keep 2,5 construction lines.
I switched all Infantry divisions to colonial template after shipping them all home. They were training till Feb 1939, and this with the Theorist gave me enough XP to construct templates... with only one small cheat (giving myself back xp used for Alpine template, as it was the same as infantry). Though it turned out unnecessary as leftover xp and fighting in Alps gave me enough to work on LARM templates before they were needed (invasion of Low Countries).
As main force I used Infantry divisions 8Inf, Art with Rec/Eng/AT/Art Support, and mountaineers with identical template. LARM (or DLM as French call it) had 3 LT, 6 MOT, with Rec/Art/Eng, and later, during 1940, I added to add SPART and Signal. All tank units were turned to this template. MOT divisions got only support (Rec/Eng/Art/AT) and I had to turn one of them to colonial inf to get the trucks I needed for tanks. Later (late 1940) they got 2xSPART.
I trained some 20 additional colonial divisions to be switched to normal inf template as production allowed, and managed to do it before war.
With careful micro, my line in Alps kept well with 20-22 divisions and air cover. Against Germans, I entered LC with more than third of my forces including all LARM and MOT, and established defensive line on Meuse. Here it also required much micro to survive, but it worked well, esp after I got NED and BEL divisions under my command. Around historical time Germans declared on Denmark and Norway, sending away some forces I managed to crush 4-5 divisions but was forced to retire, and for some reason AI decided it is too weak take to Kopenhagen itself (after taking entire island).
Holding straits proven impossible as I was unable to keep forces in Denmark. Even 2 divs they gave me could not be supplied, no matter total naval superiority (in fact, total destruction on German navy)
This also allowed British to finally land in Wilhelmshaven with 20 divisions and expand towards NED. It again required me to send forces there to stop them from killing themselves, as they expanded without taking into account the need to keep flanks covered... Thankfully the invasion, or growing number of Belgian divisions (or both) made Germans stop attacking, so I had some forces to spare.
After some time invasion stalled, and left Germans stretched out in thin but unbeakable, 1-2 prov line from Hague almost to Rhur, with east front of landings along the Weser. I tried to break out into eastern Belgium, but it turned nigh impossible, I made bridgehead on the other side of Meuse from Liege, but couldn't break out from there. Germans seemed unbeatable until my forces entered from Alps after capitulation of Italy.
One thing that I found strange, was how much effort I had to put in defeating Italians after they burned all equipment in constant Alpine attacks. Yes, they were not much of a threat, but it still took disproportionate long time to dislodge them from positions, and in times they kept never-ending attack even though they had less than 15%-20% strength and less than 10 org at all times... True that I had way less divisions (25?) against their (initially) a hundred or so, but mine were full strength almost all the time. It seems 12 20% divs can hold out longer than 2-3 divisions.
They finally broke down after they lost all manpower, from reserve and from units themselves, after I landed in south, near Taranto and expanded from there, finally reaching Rome.
I used 2 major cheats:
As AI decided to support Axis with Hungary after Second Vienna Award I was forced to reload and use console to make Hungary Allied. Why? They were pro-german and nationalistic but not suicidal. Besides, they joined war only during Barbarossa, and I do not believe they would if France held and started winning. They were not eager to be in war, as evident by refusal to give military access to Germans prior invasion of Poland, and mostly free passage for Polish troops.
I'd prefer to force them to stay neutral, but I don't know how.
I also teleported 8 Polish divisions to Africa after Poland started loosing (interesting that they held till November) and gave them myself as expeditionary force. I wanted to have Polish Army in Exile

I would agree 8 divs is a bit too much... 4-5 would be more appropriate. After securing N Africa, I gave Poland strip of land with Benghazi, as there was no other way to send LL to them, and they didn't want to take supplies straight from my stocks. Interestingly, one division got South African guns, but those could be from LL delivered during defence of Poland.
Similarly, I "saved" two invasion forces (10 and 8 divisions) UK wanted to send to die in Wilhelmshaven soon after the war started, tag-swithing and making them expeditionary. Though, as they were preparing in Pas de Calais, I consider myself excused
