I'm curious if Oda will ever reveal how the Revolutionaries tie into the balance of power. We already know Yonkou vs. Yonkou vs. Yonkou vs. Yonkou >= MHQ + 7 SB. I doubt the WG ever considered the possibility of something like the Revolutionaries allying themselves with a Yonkou (e.g. Shanks), but this is what makes someone like Luffy so dangerous--he has ties to the Yonkou
and the Revolutionaries. If the Revolutionaries were to receive assistance from just 1 Yonkou fleet, and vice-versa, how would the balance of power change? Now that is something I'd like to see Oda highlight one of these days.
Did you ever think about one of gorosei's strength may be as much as a yonko? They are old enough to see lots of war (even the war with the ancient kingdom? maybe gorosei who starts the war?). Just look at scars they have, gorosei should be above of the admiral level. Don't underestimate them.
Each Gorosei could be "top-tier", but stronger than an Admiral? Unlikely because of their advanced age, as well as Admirals being the "strongest". The important thing to keep in mind though when comparing the Yonkou to the World Government is the
total military power each side has. The WG, with assistance from the Shichibukai, can easily defeat the forces of 1 Yonkou fleet, maybe 2 if under better circumstances (e.g. what would happen if Fujitora and Ryokugya were present at the Marineford War + all 7 Shichibukai?). Still, the WG lacks the manpower to take on all 4 Yonkou fleets themselves, and this isn't factoring in the constant infighting that goes on between the Yonkou fleets.