in this blog i'm gonna speculate about about guild ranking system of the diffrent familias.
the ranking system seem to be based on 2 factor, the level and the size of the familia.we know from Hestia Familia ranking up that:
having at least 1 lv2 adventurer grants to the familia the rank H.
having at least 1 lv3 adventurer grants to the familia the rank E.
having at least 1 lv4 adventurer grants to the familia the rank D.
miach familia also only 1 lv2 adventurer (aka naaza) and was rank H, but miach activity sector is in pharmaceutical not dungeon exploration,
though thses condition are enough but not necessary for r rank up, meaning a familia can rank up to D without having a lvl4 like it is the case for Apollo Familia, they had only a lvl3 captain and alot of lv2 and lv1,
so to reach rank D a familia need either 1lv4, or a high number of lowre level adventurers, of course the number goes higher the more low level they become.
if we extrapolate, then the conditions would be: 1lv5 for rank C, 1lv6 for rankB, 1lv7 for rankA
but we know that Ishtar Familia was ranked A even though they highest level Phryne was only lv5., in the other hand,Ishtar familia had hundreds of memebers.
since the ranking of these exploration type familia is basing on their ability to defeat monsters, we know that to defeat a higher level monster, it usually take a party of about 5 adventurers or more to defeat a monster of one level higher than their own.
it would be more easy to accord scores to adventurers according to their level and the score is multiplied by 5 with every level up.
lv1=1, lv2=5, lv3=25, lv4,125, lv5=625, lv6=3125, lv7=15625
in this case a familia with a score of 125+ would have rank D
of course the exampleis is not accurate, i mean the score would go up exponentially like that, its just an example.
anyway my point is, the guild probably accord some threshhold scores for eatch rank, calculate the familia score by adding the scores of its respective members, and gives the familia its rank if it reach that score.
so more work figuring out, excactly what scores are attributed to eatch adventurer lvl, and eatch familia rank.
please do share your opinions about thsi on comments