What if the French Army had adopted the spade a few years before WW1? Would the ability to dig in more easily have changed the battles of 1914?
(I find this one fascinating because it sounds like such a little thing.)
The ability to dig a hole in 1914 is not the key to survival. It is the ability to construct top cover to go over that hole. Now there are two basic ways of doing this, one it to make a roof or the other is dig a second hole adjoining the bottom of the first hole, into which you can scramble when the shrapnel starts raining down.
For a really serious trench you don't just need to dig but have access to some kind of propping material, most typically wood but of course concrete and better yet reinforced concrete is pretty awesome.
Armies seem to have grasped the value of entrenchment in static positions and the engineers had a reasonable though of course without practice far from perfect idea of what was required.
Maybe if the spade introduction had led to the call for more battalions it might have made a difference later but I am not inclined to see as changing much early on.