Probably the silliest policy that Russia followed.
If Russia had of been willing to let Bulgaria take Constantinople (or had arranged a compromise of an internationalised city jointly under the supervision of select great powers and the Balkan states) they might have kept the Balkan alliance together and won WW1 in 2 years.
Disagree. The problem with the Balkan alliance was that they could never agree on who should get what teritory especially in Macedonia. Because of geography it was also never gonna work out:
1. They started the conflict without prior agreements on how to divide the territory. Serbia did manage to come to an agreement with Greece (as they interests did not really overlap) but there was no agreement between Greece and Bulgaria and the agreement between Serbia and Bulgaria was also such that it left a big chunk of Macedonia undecided because they couldnt agree about it (the decision was to be made by Russia after their victory)
2. Bulgaria's number 1 priority was Macedonia. But a victory also ment that it will be necessery that they wont be the one's actually occupying it as they would still need to fight the turks in Thrace while the others will be practically be done with their part of fighting. This was a huge issue because the Balkans states were very loath to give up a territory they once occupied.
3. Part of territory promised to Serbia (the northern half of Albania) was not going to get the nod from the GP's - at least not from Austria. The Austrians would have sooner started what would have probably turned out to be an early wwI than let that happen. Combine this and the Serbians also occupying the supposedly Bulgarian part of Macedonia (beyond what was supposed to be decided by Russia) and there is about zero possibility to avoid a Bulgarian - Serbian conflict.
I do understand that an Orthodox controlled Constantinople would have meant Russia could never take it but given the opportunities that it would have opened up it would imo have been worth it.
Sorry but this made me laugh because there was a point in the war when Bulgaria seemed to be about to take the city - they were stopped on the last line of defense (Catalca line) before the city. The russian reaction was to prepare a naval invasion of Constantinople and be ready to take the city from the Bulgarians if necessery. I dont know if their obsession with the city was more religious or ideological - maybe both - but it undoubtedly existed. If any of the Balkan states would have taken it Russia would prepare for war if not attack right away. Russia would not only be ready and willing to take the city from any of the Balkan States but much more likely to try to do so.
Final point that just came to mind: there was an important strategic reason for the Ottomans to retain Constantinople as well - and this one was for everyone. All existing agreements regarding the Straits were made with the Ottomans. Any new power taking them or even half of them would open a huge can of worms for everyone.