They've made a self-driving car. The merely annoying parts are going to be the fun bits! Everything else is going to be difficult, if not bordering-on-impossible. I find it very difficult to believe that there is any technical barrier to computer-operated indicators.
Wouldn't it be sufficient to wire in a computer controlled switch in parallel to the mechanical switch that the human uses to control the turn signals?
Or just add a new set of turn signals independent of the built-in ones.