The MVC Grid uses the MVC EditorTemplates and currently does not support setting a JavaScript function name for the column's "editor" property. Please consider adding the ability to set the javascript name for the column's editor. http://www.kendoui.com/forums/kendo-ui-complete-for-asp-net-mvc/grid/binding-to-custom-editor-for-a-grid-column-i-e-drop-down-list.aspx
Some of our custom editors just can't be done in EditorTemplates, or they are much easier to do with a JavaScript function. You already have ClientTemplate(), you might as well just add ClientEditor() and be done with it. That way we can use MVC Razor, but when we need to we can add a JS function as the editor. When the grid renders, you are already spitting out the JS API syntax using the "editor:" property. Please just add ClientEditor().
One good reason this is need is so you can have standard HTML inputs, elements, etc. in your editor, and not just a single Kendo MVC widget. I tried putting standard HTML (couple of checkboxes and some span elements) inside a MVC Editor-template, but there's 2 main problems: (1) when you click anything other than the checkbox (the span element, or other text) the editor is automatically closed. (2) the grid's "save" event is not fired when the editor is closed (where you could manually update the model). This can be fixed by having an "apply" button/span that the user clicks inside your editor and you can get the row's data-item model, but clicking around in the editor causes the editor to close.