The problem with a WWI game is that you need to make a major investment to get the pieces (both in time and money).
If you’re anything like me you’ll want all the pieces to really look the part so you’ll need biplanes, zeppelins, tanks, all new infantry, artillery, all new naval units.
You can use micro armour or naval miniatures for most of this stuff (1:72 plastics for the infantry) but then you’ll have to paint them all (perhaps to match some plastic pieces you’ve got). Also, this can get really expensive.
Lets face it there is no easy way to produce a complete and uniform looking set of WWI pieces for a strategic game.
The question is how badly do you want to play a WWI game?
This is why I’m concentrating my creative efforts on producing maps and variant rules for pieces that already exist.