Most of the vanilla retinue triggers for agents involved being in a settlement with a certain building or something like that. It looks like the Catamite and Pet Monkey are most common, at least in my games.

I wrote here that EB's traits and ancillaries are about 25% complete. Agent traits and ancillaries would fall into that 75% incomplete area. I'm definitely open to any suggestions for traits and ancillaries that would be:

1. Historically justifiable
2. Different from what already exists (agents only have 4 stats that can be affected by traits/ancillaries: Movement, Subterfuge/Negotiation, Line of Sight, and Personal Security).

There is a bit I've done in this area, but it's very minor and nothing compared to what I've done for generals/governors.