The DLC does not need to be centered on this, but it would be cool if it/the accompanying patch fleshed out the imprisonment and the ways of getting people in and out of jail a bit. For example:
- a CB on another ruler to release a prisoner (e.g. when you don't want to pay ransom or the ruler refuses to release the prisoner),
- a CB on another ruler to give over a prisoner/courtier (e.g. useful when one of your pesky courtiers escapes the arrest and flees to a foreign court),
- a plot to arrest your vassal with no relationship penalty (similar to revocation plot; your plot supporters represent you fabricating evidence/getting the "court of peers" to agree to the imprisonment demand),
- a plot to free a prisoner,
- a plot to petition the liege to free a prisoner,
- a plot to kidnap someone in a foreign court (with a relationship malus),
- a plot to petition the liege to imprison someone,
etc.
+1
If some Sultan refuses to give me back my son, I should be able to storm his lands Robb Start style and try to free him. Hopefully, with more success.