in tandem, sure, or in parallel, but not stuck together in a single history, esp since that would probably be the code vcs, which sucks for anything other than code. git sucks for anything that isn't code, because it wasn't made to handle anything that isn't code. translations, famously, aren't (usually) code, and therefore we shouldn't force people to use a tool that sucks for what they do
hence, a submodule like thing but across VCSs
code history and translation history and assets history aren't wholly separate, true, but they shouldn't be stuck together because, no, one tool will never work for every job, and we need to accept that and work into making things that do work