Sure. We've had dictionary software for decades.

This whole trend of adding a service to stuff that doesn't need a service is very annoying.

Absolutely. In my understanding and approach, it would need two smaller modifications:

1. making "scanning" (the clipboard capturing feature opt-in, with a huge notification for the implications

2. disabling the English-Chinese online translation plugin by default

use TLS enabled dictionary service. if there is none, you dont want this feature. at all. make sure they click through something or explicitly enable is even hard as you cannot assume a user understands the impact. they might not understand what it means to send their data over plaintext, or what someone can do with it.