Using DELETE with a Body is risky... I prefer this approach for List Operations over REST:
Regular Operations
GET /objects/ Gets all Objects
GET /object/ID Gets an Object with specified ID
POST /objects Adds a new Object
PUT /object/ID Adds an Object with specified ID, Updates an Object
DELETE /object/ID Deletes the object with specified ID
All Custom actions are POST
POST /objects/addList Adds a List or Array of Objects included in body
POST /objects/deleteList Deletes a List of Objects included in body
POST /objects/customQuery Creates a List based on custom query in body
If a client doesn't support your extended operations they can work in the regular way.