Training Cattle's model was inappropriate for Skyrim. Trained cattle in Oblivion ended up happy, but less capable than they had been as npcs. The bandit/thralls in Skyrim were not weaker or unhappier than regular bandits.
Dawnguard brought thralls who had been beaten down. Those poor cattle in the castle are pitiful. Harkon's gang are just not very nice. The other vampires are arrogant and rude if you ever get them to 'hello' you, but the condition of their thralls suggested to me that they were not as nasty as Harkon's bunch. That suggested to me that the regular thralls were not violently enslaved or mistreated in the same way. The vampire disease, Sanguinare Vampiris, is different than the disease in Morrowind or Cryodiil. In the mod, Training Cattle, npcs could become addicted to being fed upon.
In the new mod, Thrallling Skyrim, that feeding confers positive benefits improving the rate of healing and stamina recovery making the fed upon feel good. Those bandits are there in the caves because they like it there. The vampires, of course, benefit as well. Smaller drinks using the standing animations confer some immunity from the sun by increasing the rates of Magicka, Health, and Stamina recovery for a short time to npc vampires or to the the player vampire.
There exist vampires who have a different understanding of how they can conquer the sun. While the player runs about doing quests they are working to extend thralldom to the larger population of Skyrim.
I hope to have at least a beta availble sometime after the holidays.
What we've got working:
1. Vampires feed. Every once and a while, the vampires you encounter will grab a little drink.
2. The vampire attacks are not just mindless killing sprees. Unique npcs will very rarely be killed. The attacks enable a trainer/feeder to move into a town for a short period.
3. If you travel with Serana for a short time, the odds are that she will drink a little of your blood.
4. After she has fed, other vampires will recognise that fact. Pets will still be hostile.
5. The player can create thralls.
6. The player can inadvertently become a thrall gaining all the benefits without a name change. Player thralldom confers immunity to accidental infection of Sanguinare Vampiris.
7. The player's followers may will become vampire thralls (no name change).
8. Thralls, including followers, will occasionally be observed soliciting a feeding.
9. As a vampire, the player can drink from npcs just like any other vampire.
10. The mechanics of thralling the Jarls and their advisers are in place.
Normal feeding on sleepers damages the sleepers.
11. There is a downside to being a thrall. You gain from being fed upon, but if there is too much time between feedings you will be punished by a mildly unpleasant form of withdrawal.
12. The vampire game has been imported to Skyrim by some of the npcs who introduced it to Cryodiil.
To be completed:
1. As a thrall, the player should be able to help the Dawnguard destroy Harken while protecting the other vampires from the Dawnguard eventually subverting the organization. Some of the Dawnguard quest wills be subverted.
2. Created thralls should be able to take direction such as traveling to locations or following the player.
3. Thralled npcs may be travelling to visit distant vampire locations or to be fed upon by particular vampires.
4. Some of the Jarls may be eventually selected to become vampires. The vampire plotters think that vampires make better leaders than thralls. They believe that not doing that led to the Empire's defeat.
5. At present, benefits from feeding or being fed upon do not increase with experience. It is possible that they may be increased or diminished in the future.
6. Quests to benefit the non-Harkon vampire campaign besides feeding regularly. I strongly suspect that disquised thralls and vampires will infiltrate the Dawnguard whether the player becomes a vampire or not. This should be done without the Dawnguard members feeling that they have been mistreated.
7. Some way of protecting the player from Serana. Right now, traveling with her will turn your player into a thrall eventually.
8. One or two of the books from Training Cattle are going to find their way into Skyrim. They should be old copies, because Skyrim is a short in the publishing department.
Last night I was much entertained when my thrall character encountered Serana after their separation following Bloodline and received a big hug as she greeted him. Isran was unsettled, but, in the main, oblivious while she fed.