Another option could have been a negotiated peace once the stalemate was realised, maybe after the great loss of life after attempts to break through heavy defences consistently failed in 1915/16, but definitely after the Battle of Jutland showed that even a decisive naval battle was unlikely. So lets say this armistice occurred two years earlier on November 11 1916 instead of 1918, driven by an outbreak of common sense rather than the collapse of the Balkan front and the Central powers realisation they could no longer secure their southern front and had also lost access to much needed oil and food.
As peace came out of stalemate, rather than capitulation prior to an inevitable defeat, there were no reparations or territorial annexations, no forced disarmament or onerous treaties, each side basically was left to lick their wounds and get on with life. Russian, Turkish and other civil wars/revolutions would still occur as the underlying social and economic problems would still exist, but there would be no certainty of who would win and form government, nationalists, royalists, fascists, socialists or communists.
Another thought is what would have happened in the UK, would a negotiated peace have boosted the left or the right? For instance a very real fear at the start of WWI was that the Indian independence movement would take advantage of the situation and launch a revolt against British rule, instead India as a whole, including many desiring self government, actively supported the British during WWI, in the hope that this loyalty and support would be rewarded. Post war the likes of Churchill and other conservatives actively opposed Indian self government let alone independence, disappointing and disheartening the great majority of Indians who had actively supported the British war effort. Possibly a negotiated peace could have seen a softer line being taken with India, including self rule as a self governing Dominion within the British Empire, or perhaps even an earlier evolution of Empire into Commonwealth.