There have been a few later WW1 ATLs here.
I think its really tricky to have a later WW2 especially after a later WW1, with around the same number of dead. OTL it took some crazy things happening and some really bad luck to end up in that kind of world wide conflict.
There are narrow bands of tech advancement that made both wars the way they were. A ww1 20 years later could mean:
1) Defensive firepower becomes really nasty without any advanced armor or air doctrine to help the offensive.
2) Russians can mobilize, deploy and supply huge armies so no one would dare attack them, but Russia attacking somebody else takes a lot of political will and would Russia really want to attack Germany, especially where #1 above is true.
3) Air conditioning, malaria drugs, air travel advancements, oil and mineral mining advancements, agricultural advancments make European African colonies very attractive for European settlement and ecomomic jewels, making stupid wars over Balkan countries not seem worthwhile.
4) Somebody eventually breaks into the atomic age before it happens.