@jip Hearthstone solved that with 6 standard messages, especially if it is just text it shouldn't be to hard to develop, write and mod in.
- List the required messages. (Example: Prepare to attack soon, Scale up Eco & Tech, I take your lead, Follow my instructions, No / you idiot, Yes / good idea - to be accompanied with pings and general understanding)
- Get nationals to write it in every language.
- Mod in under hot menu
Tbh I might use this sometimes even without a language barrier...