That would be a great idea, but I would need to think on how I'd do that, but possibly If I allowed the json files used by the game be editable and visible by the player, aswell as add some mod entries for the translation...
I guess that might work. The only problem is that I guess the Portuguese translation only came on 1.3 update?
Edit:. Yep, the portuguese translation only exists on Terraria 1.3+, that means I would need to create a system for custom translations, in other words: That sounds like an interesting challenge.