Look at it like 1940..
As soon as the French were cut off by Guderian, the Bits ran back to their Island..
Similarly as soon as Paris falls, GAME over- British will go back to London and the Royal Navy will make a blocking stand in the channel and the north sea.
Taking Berlin as the Russian is a JOKE! - it is game impossible and in reality even the GRAND DUKE understood that it was logistically and even physically impossible, that is why the GRAND DUKE wanted to make an all out attack on Austria in the Rumelian areas (modern Ukraine/Rumania) and ignore congressional poland, the general staff also understood their limitations, ALEXEEV the Grand Duke's advisor had carved a detailed plan to such an extant.
The French gave a "BRIBE" of 500 Million Francs in late 1912-early 1913 to Russia in return of an aggressive plan, this gave rise to the famously stupid invasion of East Prussia and the disaster at Tanenberg and Masurian Lakes. Russian General Staff had made pre-war calculations that with all things equal 2 GERMAN division was equal to 3 RUSSIANs on a good day on a bad day- more Russians were needed. Taking that into consideration coupled with bad terrain, good fortresses and also the fact that- EAST PRUSSIA was the homeland of the JUNKERS- invasion of EAST PRUSSIA was doomed from the start, all STAFF officers (good ones like Hoffman, Ludendorff, Von Seckt) had their early training here, excellent railways made logistics easy and the rivalry of the Russian commanders removed whatever little hope present.
The Schlieffen plan was the best plan possible - perhaps the greatest plan since Napoleon's Austerlitz campaign plans.
It took into account Germany's bad situation and increasing weakening ally- Austria.
In 1913- Germany manged to mobilise only 52% of its men and spend only 3.4% of its money on military despite the best efforts of the Chancellors, Russian were spending 6.5%, France 4.5% and even Britain 3%. This was due to the Federal structure of Germany with Saxony, Bavaria and several smaller constituents essentially having autonomy.
France had 82% under arms, Russia had 30% (huge population's 30%).
Consider the alternate offense plans (all disastrous)- Plan XVII, Plan Conrad or Russia's Invasion of East Prussia... Schlieffen Plan looks superlative.
Had in 1905, instead of the nincompoop Moltke Jr. a stronger man become the chief like - Mackensen or Von der Goltz, GERMANY would have won in 1914.
As it was they came close, Moltke should have resisted Rupprecht's aggressive counter-attack and forced V.Hansen to move faster (3rd "SAXON" army), also V.Wurtemberg and V.Preuben (4th and 5th army - held by Crown Prince Albrecht and Crown Prince Wilhelm) moved slowly.
The really decisive march was made only by Kluck, though he has been ridiculed by the English as dumb, this was not so, he was most decisive and acted forcefully in his march. Had V.Bulow, V.Hausen and the Crown Princes followed his footsteps and stretched their armies to the end, they might have won.
Also had Moltke not panicked and sent 2 corps + 1 cavalry (5divisions in all)- including the Garde Reserve Corps (the best corps in the GERMAN army as per combat reports )
to OstPreuben, the gap would not have come between the 2 armies.. this totaled nearly 100000 troops (full strength) i.e. almost equal to the British (6 divisions in august-sept 1914).
So, the program is right- PARIS falling in 1914, which you can easily replicate once you get the knack of moving corps is correct.