One problem with 1914 is warfare on the western front. It usually just dissolves into two giant stacks going at it in one territory, and the allies win that battle 90% of the time because they can get units there faster. One reason this happens is because people aren’t aggressive enough. Also, its too easy for people to combine their forces because flanking maneuvers aren’t very deadly in Axis and Allies. So I would make on slight adjustment to the moving out of contested territories rules:
When a unit moves out of a contested territory they may not battle. They may still move into contested territories containing units belonging to their power, but they may only reinforce not battle there. Also, I was really intrigued by @Arreghas idea about contested territories. You can see his forum here: https://www.axisandallies.org/forums/topic/34163/1914-contested-territories-an-interesting-tweak