It will the same princip as is in Warhammer. Race/faction like elves is composed from multiple lords leading small subfactions with ability to confederate in-game, each one having little different effect. Basically what was considered to be culture group in Rome2/Attila with multiple factions, that is now playable faction in 3K with multiple characters leading sub-factions.
This is (at the top are different culture groups, usually each contains several factions, each such factions represented with starting character)
being converted into this (at the top you have various factions, each one with a few Legendary Lords/starting characters)