The reason companies still mail spreadsheets around is that the tool makes it all-or-nothing. Scope the invitation instead, and the freelancer you hired for Polish sees Polish.
Runs the scope they are given: invites people into it, enables locales, approves and reverts.
Writes translations and marks them reviewed. Cannot change the English source or the structure.
Reads and comments on the work. Free on every plan — a reviewer should never be a billing decision.
The same three roles, granted at whichever level fits. An agency gets a platform; a freelancer gets one project.
Viewers and reviewers never count towards the bill. Only editors do.