Could be very ugly
In 1905 the French were still operating under Plan XV, which was defensive in nature and relied on the Germans impaling themselves on the border forts, after which the French would counterattack.
And the Schleiffen Plan was not adopted until the end of the year, although it was in development. The current German Plan was to do what the French expected, and go straight at the Forts. In essence 1905 is a reverse of 1914, the Germans are doing exactly what the French expect, and will pay the price for it.
So i would expect hideous German casualties as they try to bash thru the French defenses. Whether they actually can is unknown. Schleiffen didn't think so, he thought the German artillery was not strong enough, and so decided to go around. Maybe after a year of pointless head to head bashing the germans do decide to go around thru Belgium, which may or may not draw Britain in.
Of course the germans have the same problems at Liege as OTL, and the Austrian heavy seige guns aren't built yet, so the Belgians may well be able to hold them off until the French can reinforce them. There certainly won't be any glorious and swift german victory. Given that in 1914 the Germans had 7/8ths of their army in the west and the French did exactly as they expected, i don't see the Germans doing better when the shoe is on the other foot.