Sorry about the delayed response. Have been away from the forums for a bit, but have done a lot of work on the game. Time period is basically end of the republic/beginning of the empire, but this is an alternate world so it's not exact. The playbooks are pretty well set for now and follow much of what you suggested. They are: aurores, decanus, gladiator, hastati, magus, medicus, praedo, triarii, velite, and venator. The magus playbook is the only one that needs significant work, and that's mostly the arcanum (spells). Many of the threats are classic monsters like the chimera or gorgon, but also gangs of celtic-like warbands and natural (ish) threats like haunted forests.