I thought of a mod idea that basically allows the player to find people, and turn them into Vampire thralls to be sold to Castle Volkihar, in a similar manner to how you could capture slaves for Paradise Falls on Fallout 3.
I thought maybe you could talk to a Thrallmaster in Volkihar Keep, and he will give you a spell, which allows potential thralls to be stunned, and then you zap them with another spell which teleports them to the keep. On return you are payed around 500 gold for doing so. Obviously if you are caught doing this then you would get given a 1000 gold bounty.
Maybe as an added touch they appear in the cages where the rest of the thralls are kept in the Castle, in rags and with standard Thrall dialogue.
In order to avoid glitches I also thought it could maybe limited to people who aren't essential, and those who are would simply "Resist" the spell, without a bounty or anything.
I have no modding experience at all so I don't know if you could do this practically, but I just thought it would be an awesome way for an evil character to make some money, and make it more worth your while to join the vampires over the Dawnguard.
So, any thoughts?