Financier, naval blockade, land campaigning on the periphery of Europe, you know basically everything they did IOTL without having ~50 divisions in France.
So if the Germans take the defensive in the west, it removes 3 frontline Entente armies from the continent in the west, while preserving German strength that would otherwise be frittered away in an advance through Belgium, Marne and matters relating thereto. Is that not an overwhelmingly decisive victory for the CP powers in the west?
In respect of Britain the banker, if northern France is wholly in French hands and the western front is limited to the narrow German-French border, the French finances are far less dependent on British bankers, who like the British Army, are substantially redundant in this scenario.
The OTL technically illegal blockade of the continent will be more difficult to implement from a logistical perspective and more difficult to sell from a diplomatic perspective if Belgium and Italy remain neutral and German reputation remains intact. The OTL blockade only started to bite Germany in 1916 and many have argued the silent dictatorship was even more damaging to the German economy. In this scenario any British blockade is more porous, the battlefields stacked in the CP favour - the silent dictatorship stillborn.
The British land campaigns on the periphery of Europe are not going to trouble the core CP powers, but are interesting to contemplate. I could see the British pushing the Ottomans back to the periphery of Anatolia some time in 1916, but I think the scenario almost encourages an earlier and supersized version of the OTL cluster f**k that was Gallipoli. The problem with the periphery is British amphibious ineptitude was an unknown, and coupled with Churchill's 'genius' is likely to result in truly memorable experiences for the British...
Again, I doubt the Russians will be thrilled with the perception of the British ignoring the Germans and instead attempting to advance British interests in areas sensitive to Russia...