Have they checked the Native language filter construction feature?
(The ability to formulate filters using compact, native language constructs)
Instead of:
PredicateExpression.Add(new FieldCompareValuePredicate(OrderFields.EmployeeID, null, ComparisonOperator.Equal, 2));
You can do this:
PredicateExpression.Add(OrderFields.EmployeeID == 2);
This can be quite handy in many situations.
Also if something gets too complicated, they can fall back to stored procedures and or database views, and call/map then from LLBLGen Pro.