I will for the most part preserve what is in vanilla, or use the same numbers for equivalent technologies, and simply add to it to extend the timeline. There may be differences in the historical year, though. One of the few exceptions is the Volksturm doctrine. That will be axed, as it was in the DDA version of the mod, because the AI of German puppets researches this even if Germany is winning the war.
Take a look at a preview of the navy tree. I still have to do destroyers, light cruisers, heavy cruisers, and amphibious assault vehicles. The blank space at the right is reserved for aircraft upgrades. After the 1960s, carriers were built for a 40-50 year service life with only aircraft upgrades.