Besides, Germany in this scenario does not NEED Japan at all, so it has far more to gain in the East by retaining a state of war until Japan's allies crash, then demanding its territory back at the general peace conference.
I would agree, but this reminds me of raising another point. I think that the most likely sequence ITTL sees Russia collapsing in revolution first in late 1915 to early-mid 1916, then France be overrun by overwhelming concentrated CP manpower, with coordinated German-Austrian offensives breaking out towards Paris and Italo-Austrian ones towards Marseilles in early to late 1916.
In your judgement, when France collapses, would the Marine Nationale surrender to the CPs as part of the armistice, or would it try and escape to Britain, or possibly would France collapse in revolution too like 1918 Germany ? Russian fleets most likely are swept in disarray by revolution and are unavailable to CPs and Entente alike until the RCW is settled one way or another. By the way, would the CPs still send Lenin to Russia ITTL ?
Since after France and Russia collapse, Britain almost surely swiftly asks for a compromise peace, otherwise in the long run the CPs could sweep British forces out of Africa and the Middle East and threaten India. Yet, combined CPs navies alone may or may not be able to blockade the British Isles, which would be necessary for the CPs to force through a really harsh peace. Possibly a substantial naval build-up program by the CPs would be necessary. So it is questionable whether the CP governments may afford to remain in a sate of war for the lengthy time necessary, or would settle for giving a relatively lenient peace to Britain, and spare the Brest-Litovsk/Reverse Versailles harsh stuff for France and Russia.
OTOH, if the CPs can seize the Russian, or, much more so, the French Navy, then surely combined with their own Navies they would have the means to blockade the British Isles and impose whatever harsh peace they fancy to Britain.
The same reasoning is valid, to a lesser degree, for Japan. Once the Entente powers are done away, one way or another, they would be forced to beg a peace, lest the combined CP naval might sweep them away, but if they beg a compromise peace after France falls, they might get a status quo ante peace, if they wait after UK falls, they would have to give more painful concessions (e.g. losing Formosa or Korea).
Romania was a vital economic asset to Germany, hence in OTL Mackensen ending up being based there to co-ordinate things despite his huge skills as a strategic commander in the field. If Romania throws in with the Central Powers (not certain, since there were very close Russian-Romanian ties at court level) then Germany gets a great boost from their economy fully joining the war effort.
About Romania, well, they waited a couple years before taking the Entente side, ITTL doing so after all of Turkey, Bulgaria, Sweden, Italy, and quite possibly Greece going CPs, if the same time schedule is kept (hard to see reasons why Romania would have to join the Entente quicker than OTL), would entail a serious mistake in judgement from Bucharest. Transylvania is surely enticing, but after Italy joins CPs, they shall have plenty of spare troops in the Balkans to overrun Romania even more quickly than OTL. May Romanian government be so overconfident as to be oblivious of this ? Would the ties you quote still be able to do it, or at least keep Romania neutral ? Since a CP victory at this point, even if Romania stays neutral, means they shall have to give back Dobruja to Bulgaria and forget any aspiration on Transylvania. OTOH, if they go CPs, they can at least have a realistic hope of regaining Bessarabia and chunks of Transinistria, so their own best self-interest would seem to join the CPs.
The harshness of the peace deal that Britain gets would vary according to the butterflies above, but I would expect defeated France and revolutionary Russia still to get a rather harsh Reverse Versailles/B-L deal. After all, even if TTL's WWI would be rather shorter than OTL (most likely, even Britain and Japan give up by late 1916 to early 1917), under the most likely PoDs (Italy joins in 1915 after successful negotiations with the CPs, or Germany goes East, UK stays neutral, and Italy joins in 1914) still it would entail 2-3 years of total war, most likely enough to harden CP public opinion substantially against the Entente powers.
However, ITTL Lenin may or may not go to Russia (without him, leadership of the Reds would likely default to Trotski), the B-L settlment would stick, and the CPs may or may not still have the energy to make a large-scale intervention in the RCW, and cast victory for the Whites.
