Since the objective is a stronger Russia post WW1, let m propose a POD somewhat earlier- a Russian victory in the Russo-Japanese war. It was a close run thing that should have been in the bag for Russia if not for serial incompetence and unluck on the part of both their army and navy and the desire to focus on unrest in Russia proper. Even if with all that Japan was so financially strained that they could not have sustained the war for much longer-all Russia needed to do was hold on until Japan caved.
Then WW1 roles along, and Russia manages to hold on until the end(perhaps due to the Ottomans not making the entirely stupid decision of siding with the CP, thus leaving the Bosporus straits open).
Britain has now warded of the German threat, only to be faced by the other national nightmare of the Russian Bear dominating Eurasia. The two major buffers against it in Europe- AH and Germany- have been demolished an crippled respectively, Russia will be eying Constantinople which was promised to it as the fruit of it's labour in the war, they are occupying Northern Iran and China(probably having seized Germany's China concession and extended it's sphere of influence to Beijing whilst China is to weak to resist and Britain is distracted by European war) and Russia's industrialization, economic and population growth is continuing apace absent the disaster and derailment of communist revolution.
Now I can't see Britain and France starting another World War so soon after the exhaustion and suffering of the last one- Russia might be more willing to do so given how they're despotic and militant. But on the other hand Britain will surely be severely concerned by the need to maintain a balance of power against Russia- perhaps by their old strategy of propping up allies that will do their fighting for them. Unfortunately with both Germany and Japan curb stomped they will have precious few candidates for that role- perhaps trying to restrain France's impulse to weaken Germany as much as possible therefore leaving Germany stronger, bolstering the Ottomans and trying to prop up a nationalist anti-Russian regime in China may be their only options. And they might grant India greater autonomy earlier for fear of Russia co-opting the independence movement as a proxy.
But without nuclear weaponry-caused MAD this unstable balance of power must surely fall apart and lead to another war at some point- very probably the basis for WW2(should their be an event known as such in this TL). I can't really see the Brits standing much chance at holding Russia back in China or the Middle East, but if a coalition of Germany, France and Britain can be formed then they might be able to counter those gains by threatening Russia's European territories...