That's something I proposed a long time ago (and still just an idea): integrate the language editor with whatever translation tool we are going to use.
Transifex has APIs:
Use the APIs requires a Transifex account.
So, the easy way is to just ask people to register and push their suggestions directly to Transifex.
There may be a way to suggest translations even without a Transifex account: the original plan to use github and its APIs to open an issue to a specific repository or to the main repo, but with some way to differentiate from the normal issues.
Something to think about. ;D