Have you considered implementing user impersonation for administrators? Allowing admins to impersonate end users would make troubleshooting and resolving issues more efficient. It would also help in testing roles & permissions from end to end.
I don't really see the need to impersonate users in Dataiku. On one side it's to test roles and permissions using other users, either LDAP or local. With regards to user permissions I can easily replicate a user and have the same permissions as them.Most of what users run for real is in Scenarios. Scenarios can run as any user you want so in effect you can impersonate them already in a scenario. Then you can also impersonate a user in the Python API using the user.get_client_as() method. Finally you could integrate with SAML or OpenID Connect which means you can add an impersonation backdoor at that layer. So I think you got plenty of opportunities for impersonation in Dataiku. If the above options don't cover your needs then please expand on your use case and why you think you need to impersonate a user.