Arya was already warging, by the time of Clash of Kings having her wolf dreams. Jaqen knows about this, because he had studied her.
Tell me, what other value does Arya bring to the organisation? She can't become a Noone and she is reckless.
Her warging capability is her only advantage.
Look, I know you're gonna say "the tv show doesn't have her as a Warg" but this is an adaptation of the books, just because D&D create these plotholes and badly motivated characters, doesn't mean we readers, cannot fill in these gaps of logic, with the source material.
Saltpans was the closest port from Harrenhall, book wise this makes sense that the Faceless Men ascociate would be waiting for her, tv wise it doesn't make as much sense due to the Vale plot.
Are you telling me an unimportant port like Saltpans, out of all the possible ships is just a coincidence that it's a Bravoosi ship?
This is also why Rorge & Biter we're searching for Arya and why they burn down Salttowns.
Good for you?

Since you saw the original post, I'll stick with my recommendation. Re-reading the Arya chapters and Feast for Crows Brienne chapters answer your questions.