By now it's widely accepted that the Schlieffen Plan was flawed. It used unexistent divisions, overestimated the physical capacity of soldiers, the Belgian resistance, and didn't take into account the retreating armies destroying railways. The logistical situation was also downplayed.
So, the question is, can these issues be solved with minor changes? Or would you need an earlier POD and more fundamental ones?
Mechanization is possible, as is having more RR rolling stock, locos and track workers to make sure that logistics work. Otherwise
you are stuck with 1870 horse drawn mobility.
Even that would have been enough if they were plans for a 'Special Forces' to grab vital bridges and that.
Communications, could have been better than wire telegraph, spark gap radio transmitters, and carrier pigeons
Amphetamine was discovered in 1887, so is possible to keep those guys marching, if needed.
But to me, all of that still doesn't guarantee a fast French knockout. Look how long France held out, after the disasters in the field in 1870 and Paris under Siege, and that was without the UK and Russia in the mix
The only real chance the German have, is to stay on the defense in the West, while giving the Russians enough of a bloody nose to get some kind of peace talks going by Christmas