I've started working on a hack set in an alternate Roman Empire where magic and mythology exist. The Empire is just beginning to stretch into the neighboring lands and meet mysterious and dangerous foes. The characters are grouped into a small cohort, a special forces unit of sorts, and tasked with discovery or elimination of a threat (or things along those lines).

Probably will include mass combat rules as well.

Has anyone already worked on something like this? Any comments or suggestions?

Thank you.