Hi first off I like the alt history setting for Tannhauser WW1 still goingon in the late 1940's, but to me right of the bat there are problem to exstending the Great War. It was a real meat grinder of one, a war like that requires manpower, money and supplies like food in regular amounts. Both sides would use great gobs of it. Also the fighting would degenerate each year to a min of 3 or less major pushes a year between in no man's land between each side's trenchworks.
One thing that Tannhauser left out was Mexico and the 1917 Zimmerman telgram and Imperial Germany offer that if Mexico attacked USA, the Germans would offer some support battlewise and help them regain some of the original USA Mexico land. The problem is that the ABC nations in South America would have risin up againest the Hun if Mexico attacked or invaded the USA.
This Fench game and setting does seem to mention what it's like homeside for each side that fighting in this war, Volstag Act which happend in the USA in the 1920's really started in 1917 when the USA Army was conviced by the anti saloon league to ban strong spirits and beer from army bases and the men from being in bars overseas.
What I mean is that like in WW2 there would be a black market goods, such a ration stamps, and the food and drink that hard to get.
LW