Way to set all queries to run through SSEM to READ UNCOMMITTED?
If by SSEM you mean SQL Server Management Studio (SSMS), there is an option you can set when logged in as this user to run as READ UNCOMMITTED by default:


  


But they could easily override that by unchecking the box, setting their own isolation level manually, or calling stored procedures that override. Features like Resource Governor can control a lot of things, but I don't think there's a way to hard-code isolation level for all queries a user submits... 

Though, this post might be useful:


Can I force a user to use WITH NOLOCK?