One additional way to widen the war: Seeing the Russian Baltic fleet transit around the Horn of Africa, the Japanese have warning the Russians are coming and that they are stopping off in German and French ruled ports to re-coal. Not wanting the Russians to get so close to Japan as tsushima, the japanese concentrate their fleet around Taiwan, and then pounce on French Indochina to deny the Russian Baltic Fleet coal and facilities stored there and to steal it for themselves, while the Russians. Japan's attack on French Indochina activates both alliances now that Japan is fighting two enemies now instead of just one.
In a Franco-Russian versus Anglo-Japanese war, Germany has a few options:
Though it was supportive of Russian Far Eastern policy, Germany is not obligated by any signed and ratified alliance to help Russia or France in a war, so it will be neutral unless it deliberately decides to declare war on one side or the other.
So, a neutral Germany can:
a) sit and be happy making money from both sides and building up its fleet, while the country remains at peace.
b) use the moment to press colonial claims, not directly against the empires' of either belligerent but against weak non-European states. The first that comes to mind is Morocco. The second is Siam [although here, there might be some Franco-British fighting at the Indochinese-Burmese border, but I kinda doubt it because it is remote as hell and very far inland.] Grabbing a piece of China like Hainan island might be a way to go too. Maybe Italy could coordinate with Germany in all this, and pick this time to invade Libya [not sure they were militarily ready].
c) use the moment to do a colonial landgrab from one of the weak European neutrals not under the protection of either the Franco-Russian or Anglo-Japanese alliance.
Portugal might be the most tempting target, as it occupies a marginal position in Europe, far from Germany. Its African colonies could be tacked onto the German ones, and perhaps East Timor as well. Alternatively, Germany could do a "humanitarian intervention" against the Congo Free State [but not metropolitan Belgium], and get a Mittelafrika sea-to-sea corridor running from Tanganyika to the mouth of the Congo or even to Kamerun. Or it could snatch the DEI.
A Germany aligning with Russia and France cannot expect to get much territory on its own, and it puts more of its overseas territories at risk, but it can deepen economic influence over Russia and the continent and embolden the Russians and French into prolonging their war with Britain.
A Germany aligning with Britain, can probably gain some favorable border adjustments in Poland and Lorraine (Briey-Longwy), hurt the French and Russian militaries and be able to increase some of the orange territory on the map of Africa, mainly at the expense of France.