OK, the first thing you should be aware of is that what people including us call the Schlieffen plan has no resemblance to the majority of ideas and maps you see all over the web and in books. Schlieffen developed the whole right wing offensive in 1905 but Moltke only started making it into a plan, with units allocated, train timetables drawn up and the like from 1911 and it was adopted as the only German war plan from 1913. It's best to ignore the sorts of maps you can easily get hold of, they're wrong.
Secondly, apart from fighting in entrenched position the French were not the equal of the Germans when facing them in open battle, which is why Lanzerac's 5th Army kept being pushed back. Pitting 2 French Armies and the BEF and maybe the Belgian Army against the German right wing in Belgium would have been a better course of action than Plan 17 but the Germans will still push these forces back and most likely break them up, the Belgians will almost certainly retreat to Antwerp and the BEF will not retreat in lock-step with the French. There will be no battle of the Marne, but the decisive battle will occur in France, not Belgium and certainly not Germany, the Germans were simply too good in a 1 on 1 scenario for that to happen.
Not what you want to hear, no doubt, but there you have it.