I can't really provide an overarching view of the role of the translator for two millennia, but I would suggest you pick up Natalie Rothman's fantastic book Brokering Empire. Rothman examines three intermediary roles in the Venetian state of the sixteenth and seventeenth centuries as they appear in official archival material: the mercantile broker, responsible for mediating trade with foreign merchants, converts, and the dragoman, or interpreter. Reacting against a traditional historiographic narrative that assumes the division of two groups in the social imaginary predates the creation of intermediaries to bridge that gap---i.e. that the gap between cultures is a static construct, and that `liminal' intermediaries are an imperfect solution applied to an unavoidable problem---Rothman argues that, although some degree of difference is necessary to precipitate the process, the gap in the imaginary is in fact created by the intermediaries themselves, defined through the performance of their identity and the engagement of the institutions of state with that performance.

It's a dense book, and it only covers one aspect of your question, but it is an excellent way into your question.