What would Turkey lose by abandoning Montreux?

What are the advantages and disadvantages for Turkey of abandoning the Montreux Convention?

Abandoning it would make Turkey's position harder by forcing it to choose between contested unilateral rules and freer passage for large Russian naval forces.

In this assessment, abandoning Montreux would make Turkey's control of the Straits more difficult. A replacement regime would probably require unilateral Turkish rules, and whatever rules Ankara chose would displease someone. Completely free passage would remove that control and let Russia move large forces through whenever it wished. Russian actions against Ukraine, described as a Turkish friend, make that possibility a Turkish security concern. Retaining the convention lets Turkey refer to an existing set of tonnage and warship-passage restrictions.