There has only been a slight scratch on the surface of the vast WWI potential. There realy isn't much out there compared to WWII or most other periods of time except maybe the renesaince.
Just to do the three basic combat arms for all of the major players, lets say France, the Britsh Empire, The German Empire, Austro-Hungarian empire, The Ottaman Empire, Russia and the USA is is 24 sets. Maybe Italy too and that would make 27. As in WWII, in WWI, for many like France and Germany but also others, there is a late and early war look. The British would warrent Highlander units, Indian units and Australians. All of them will also need chemical warfar gear. The area of vehicles has barly been tackeled by the industry. Then there are all of the significant other nations and colonial troops.
WWI is huge. I love Strelets and I love Hat too. I'm not so sure about Ehmar but I'm still trying to get them all. We need to get Zvezda and some others in on this too