Just posting this here as I had done on Reddit, with changes as needed.
Guard Captain
Place this thrall at a desk station to gain a damage % increase for all Fighter/Archer thralls you have placed on guard within a radius of around 20-30 foundation blocks in size. This aura works similar to the Thrall Pot and Feed Boxes. With the Captain providing morale and leadership to your thralls. The radius doesn’t need to be larger, as with larger bases and more thralls, you would need more Captains to lead them.
Beastmaster
This thrall is out in the world with a pet animal, somewhat related to their race. Such as a Darfari Beastmaster might have Crocs or Hyenas, a Nordheimer up north might use Wolves. You could place this thrall in an Animal Pen to speed up maturation time for your pets. Further, all pets in the Pen could receive a damage buff for being under his teaching and care that lasts perhaps 10-15 minutes of play time. Maybe a 5-10 percent increase, nothing major. The buff would pop in like regeneration for health.
Mason
The mason thrall could have a crafting station related to foundations, fences, walls, ceilings, etc. T4’s could give the material cost reduction benefit as well as increased crafting speed similar to other crafting thralls.
Hunters
Wandering NPCs that actively hunt animals. They could be an alternative Archer thrall and function the same, with ranged damage mostly via bows.
Farmers
These thralls would also come with a new Feat, that being the Farm Plot, a planter closer to the ground and 2x2 foundation blocks in size. The Farm Plot works like a Crude Planter at it’s base state, slow growth and compost required.
However, with a T1 Farmer, it now has the growth speed of a regular Planter, and still requires compost. A T2 farmer would have a growth speed between Crude Planter and Planter, but would require no compost at all, it would passively grow things.
A T3 Farmer would have a growth speed between Planter and Improved Planter and not require compost. Lastly, the T4 Farmer would have Improved Planter speeds and not require compost, but if you choose to add compost, you get an added benefit of double the harvest.
The Farm Plot would not be placeable on foundations, it would have to be directly on the ground. To craft it would require compost, plant fibers, spikes (for plant stakes), and wood/stone for a border. The Feat would be available after Improved Planters. Being 2x2 in size, it could hold four plants at one time.
Ideally we’d be able to use seeds as “fuel” and have them grow slowly over time, giving us a slow rate of whatever they grow. Rather than how the normal planters work.
Assassin
Zamorian Thief armor mentions those remaining hidden in the description. Ideally we could have a station where an Assassin would allow you to craft poisons that could apply a buff to your weapons for short periods. Maybe something like 5 minutes; things like increased damage, tranquilizer venom (only useful to increase Truncheon damage to thralls), maybe stamina damage to use against players, damage-over-time effects. Crafted using parts from spiders, scorpions, and other venomous things, including flowers as well.