A sketch of what I would do:
/data/en/team.toml
/data/de/team.toml
{{ $data := index .Site.Data .Site.Language.Lang }}
{{ range $data.team }}
...
That and variations of the above should be pretty flexible. I don’t think /data will ever be a first class citizen of the multilingual feature, because most of its use is by nature cross-lingual.