To be honest, I dont think Oda would try to break the M3
I Believe the reason why Oda had to delay Jinbe's recruitment is due to that.
Oda gave power ups and significant experiences for both Zoro and Sanji to grow before he let Jinbe join.
Zoro now has Enma, and beating King would maker his name more prominent. The same could be said with Sanji.
their names would become more notorious than jinbe after this arc because they're a growing force, and have yet to reach primes. They will become new threats whereas for Jinbe, everyone, the marines, the govt already know what he can do. He would be less of a threat in their eyes.
as for Yamato joining, the govt know nothing about her, I assume, so the only threat Yamato has is by being just Kaido's son. So as far as the treatment to these characters are concern. The marines and other pirates would see shs strongest forces are the trio since they already have made a name for themselves as the crews main forces.
as for the power levels, if sanji and zoro develop new skills while fighting the all stars then it would be easy for me to put yamato as fourth strongest.
after all I think Yamato have yet to touched her potential, and I dont think hes above Jack at this point