Or prevent one. You know, having a valuable hostage.
We don’t know the Alliance’s plans for Talanji in that scenario, because they were never written to have any plans. There was no need. Talanji was captured for one reason, and one reason only, and that was so that the Horde could rescue her, forcing Rastakan to be indebted enough to the Horde to grant it a presence in his city, let alone the time of day.
We can speculate on what plans the Alliance could’ve had for Talanji. Given she was in a bog standard prison cell and not kept at the castle like a prisoner of high birth should have been, I can’t imagine it was anything diplomatic.