A good freelancer mod for Bannerlord would definitely need to be expanded upon, and not just be a carbon copy of the original Warband mod. As much as I love the idea of starting as a follower and working your way to the top, I found the Freelancer mod to be incredibly stale from the lack of events outside of battles and sieges. I believe that the mod Aut Caesar Aut Nihil for Warband would be the best example to follow for a good Freelancer experience.
It basically has:
- A unique rank up system that uses "progress points" instead of experience to rank up, which can be obtained through different ways that I will mention.
- Daily Trainings, Hunting, and Patrolling (could either go smoothly or be ambushed) are options through which you can passively earn progress points.
- Moral decisions that will either improve your reputation or give you progress points at the expense of losing reputation. Ex: Prevent fellow soldiers from pillaging a village or join them.
- Unique interactions with other soldiers that will either make you gain or lose progress points. Ex: Fistfight with some random drunk or snitching on a sleeping sentry.
- Once you reach a certain rank, you have the opportunity to command a certain amount of soldiers in battle. This could be tied in with the Sergeant system in Bannerlord.
- The opportunity to be recommended by your commander into elite divisions, such as Praetorian Guard. For a medieval setting, this could be the equivalent of joining the king's retinue. Similar to the Praetorian Guard experience in the mod, the player would be given a greater insight and involvement in the political realm as they carry out the duties of the king.