One of my first group rps I did here was like that. The DM had used her novel as a basis of the world and had a lot of characters running around in it like...everywhere. It was kinda fun though. It worked well for that plot and I think as a participant, it's a good experience. The most main characters I've played though is four. I am comfortable playing a whole world though. I will probably add it multiple side characters as time passes.