The Grid already has beforeEdit event that can be used for preventing the editing depending on custom logic. The same thing could be used for preventing add or delete based on custom logic or validation.
same way "beforeChage" like event is needed. It increase too much lines of code without these events. http://kendoui-feedback.telerik.com/forums/127393-kendo-ui-feedback/suggestions/32928568--changing-event-in-kendo-grid