Or maybe they just love one peculiar crew. As an example, if I would play Arcanist, it would be only to play stuffborg (steamborg, ramos arachnid) because I don't like the chimera and am not a huge fan about rasputina. As I play, let say in a fluff way, I refuse to take mercenaries (except when I think it makes sense) and to take some minions from the chimera and rasputina swarm.
So I have Ramos and my constructs, and will have to deal with all different masters with that basis.
It's not because the faction has several masters, and so several possibilities, that you want to play all of them, when your opponent could love his faction as a whole, and play with them.
This part is a little weird to me (I mean, for a tournament for example, if there is a young player with only a crew against a guild player with all the guild range of models, it makes the game pretty unbalanced, as one is over adaptative).
So I would prefer the classic system of a I have a crew and a little cache of minions and build my crew from that each game. I think it makes you think more in terms of balanced crew and allow to make disappear most of the unbalance that could exist