As of now, Ark only queries the user for "overwrite files" prompts, but this handling should be expanded to detect all prompts and send the answer back to the standard input.
What other prompts are there?
Changing the default assignee in the currently open Ark bug reports to me.
The rarplugin now handles the overwrite and password prompts, as well as several error prompts such as wrong password, CRC failures and missing volumes. Closing as fixed.