LATIN, please! Should be easiest of all languages... and never needs updating, except for general accuracy improvements. Then ELIZABETHAN ("Early Modern") ENGLISH, because a ton of that is in the public domain.

Works great so far.
It can optionally "Translate this tab automatically as you browse".
I also like that it is created "By Firefox" :)

i really like your browser, but because there is no russian, i sometimes use chrome. Please add it faster

This is a really great extension. Feels great to not use any cloud even if it's slower.
The only thing that could make this better is shortcuts. If you can just select text on page, hit a shortcut and then it translates, then it would be literally the best.