Postgres 10.5: Granting full schema access to a user that isn't the owner
Ok figured this out after doing a few more searches. 

Essentially you need to grant same role that eventually will own the object to the user you're using. 

So in my case: postgres is the user that I want to be my "pseudo-superuser" and schemaadmin is the user role that will own the objects. 

GRANT schemaadmin TO postgres;


After that, everything that schemaadmin owns, postgres can modify.