What could be cut to finance the continued war? Less materials to Italy for one stopping the largely pointless offensives in the alps for one, creating a proper defensive line of their own rather than continuing what had become easily predictable attacks,
How does that help?
If Italy stays on the defensive, that just releases Austro-Hungarian troops to tither
a) Reinforce the Germans on the Western Front, or
b) Take over more of the Russian Front, thus releasing German troops for the West.
This doesn't reduce the cost of the war, just transfers it - robbing Pierre to pay Paolo or vice versa.
bringing in more colonial troops to release manpower for agriculture and industry.
Invite greater Japanese participation in Europe that was rejected for various reasons in our timmeline and finally with having the war cost 3 million rather than 5 a day the Entante is still outspending the Centralpowers.
Where does the shipping come from?
Keep in mind that without US imports the Entente is already having big problems with shipping. Frex, if it has to import food from South America instead, that roughly doubles the journey time, so they either make do with only half the food in any given month, or else have to somehow double the number of ships. This will be hard enough without having to tie up even more shipping to transport Japanese or Indian troops halfway round the world.
There's also the language problem. How many officers does France have who can speak Arabic (or Senegalese or whatever)? How many has Britain who can speak Indian or African languages? And they'd have to be continually replaced due to the huge death toll of junior officers on the Western Front.
Seems to me that the only readily accessible source of "colonial" manpower would be Ireland. And had conscription been extended thither, the resulting fireworks hardly bear contemplating. Iirc [1] Britain did pass a law to this effect, but never dared bring it into operation.
[1] Field Marshall Haig was very keen on this idea, not just for the manpower but "for the good of Ireland". Please, please don't ask me to fathom what he meant by that.