I suggest adding a FieldExpression property to the GridColumn so a developer would not need to create view models and templates for simple transformations of the existing model's properties. The field expression would be used for filtering and sorting as well. Its type would be Func<T, object> or Expression<Func<T, object>>.

   <TelerikGrid Data="@Persons">
            <GridColumns>
                <GridColumn FieldExpression="@(p => p.FirstName + " " + p.LastName)" />
            </GridColumns>
        </TelerikGrid>