The wiimote is designed to have an unintimidating control scheme, the button count is fine. But yeah, the classic controller plugs into the wiimote, so there may be some applications that will use the traditional button layout in addition to the WiiWand.

Besides, if it is a turn-based affair, you really only need 2 buttons: one to select an option, one to cancel the selection. Even the 'cancel' button is optional if the menus are laid out well enough. It would be a problem if the Wiimote were the only possible way to control games on the Wii--something Nintendo wouldn't be so silly to do. The fact that the controller can be expanded upon removes any potential problems with the button layout--in theory. While true that you can just plug in the appropriate controller, the hindrance will be obtaining that plug-in peripheral if you don't already have it.