I was recently thinking about how to incorporate the various ancient forms of divination (such as such as extispicy, haruspicy, augury, and astrology) into the 2nd Edition magic system for use in Bronze Age era adventuring without re-inventing the wheel and adding in a whole new system of magic. I’ve been thinking that the best way to do it is to add in proficiencies for each type of divination, and require the use of them with the spells, and using the requirements of those proficiencies to replace most of the existing material and somatic components of the spells. For example, to cast a divinatory spell using the Extispicy proficiency, a priest or wizard would need to examine the entrails of an animal of some sort; it would make sense that a larger animal would be required for higher level spells (birds for low level spells, sheep and goats for mid-level spells, and bulls for high-level spells, for example).
The main goal with this is to add flavor to a game without actually changing the rules. Obviously, in this world, such divinations don’t really work (although haruspicy and extispicy can identify some aspects of poor health in local animals, which could indicate the area is poor for whatever plans the people have), however, it makes sense that in a fantasy version of the ancient world, they would work. One thing that should not be done is making these types of spells any more explicitly difficult to cast, or no one would want to play characters who cast such spells.