What exactly does a Panzer I do if it encounters an FT17? Its 8mm machineguns can't hurt the French tank, so all it can do is run away. An anti-tank rifle will easily put holes through the armor of a Panzer I just as easily as through an FT17. The FT can at least fire a small explosive round against enemy infantry positions. Less obsolete than the FT17, perhaps. More useful on a 1939 battlefield, probably not. That's why most of them were later converted into self-propelled artillery or tank destroyers, and the rest used only for training purposes and backwater garrison duty.
The rest of your post about production optimization I agree with. France was not set up to produce war materials at a wartime pace, Germany was. Given time, Germany would eventually have had to reduce its pace due to several major factors (some of which were historically band-aided by the conquest and subsequent use of French industry and transportation), while France could have increased its production considerably, outpacing Germany's faltering industry.
Exactly what Herbert West said.
If a Panzer I alone for some reason encounters a FT17, it reverses and go somewhere else. Same if it meets most of what the French had (B1Bis, R35, H35, D2). What can the FT17 do ?
The Panzer I has anti-infantry weapons, if it is facing a tank something went wrong. The only thing it has to avoid is a Somua S35 or a Panhard 178 - or rare stuff like AMC35.
If the FT17 meets any other German armor than a Panzer I, it is toast.
But the Panzer I doesn't have to be alone. With its speed, it can follow & support heavier tanks like Panzer II or Panzer III. Meanwhile, if you mix FT17 with anything else, then you have a tank unit with a speed of 9 km/h and an operational range of 60 km.
So back to your hypothetical case, if a Panzer I encounters for some reason a FT17, it will reverse and then the other Panzer II or Panzer III nearby will destroy the FT17.
Against infantry, Panzer I (and half of the FT17) have machine-guns which kills infantry about as well or better than small explosive round, but it can also overrun said infantry and attack them from an unexpected angle. If a FT17 comes to your position well, first with its speed and operational range you know that they are coming to you so you are prepared, and at worse infantry can just flee (and abandon equipment) while cavalry (still a thing in 1940) can retreat WITH equipment.
As for using anti-tank rifles against a Panzer I, well - tough luck - the French had none, except a few hundreds given by the Brits in 1940 and that barely reached the frontline. Also, whoever is handling that Boys has better be heroic because he will be on the receiving hands of quite a large volume of machine gun after his first shoots.
Bottom-line :
- The FT17 was totally useless in 1939 - 1940 except for static defense.
- The Panzer I was obsolete but still somehow useful.