Sadly there is no way (for mods, admins etc.) to change other people's vessel crew. That could be useful - e.g. when someone sold their vessel and forgot to add buyer as a crew (or forgot to remove himself).
The only way we can do it right now is to use console command - and my staff hasn't (obviously) access to console.

This is something I have wanted to add. Its actually cased by the shipIdArgument not having a override state