Feature templates should work fine with Single Symbol. So, you are saying that you cannot create any templates for a Single Symbol layer? I just want to make sure that is your problem, rather than templates existing on the Organize Feature Templates dialog but not displaying on the Create Features window.
With the unique values renderer, you generally cannot use templates with <all other values> since the features would not be properly symbolized or attributed and would disappear once you create them. The general philosophy for templates is that the features created with them must be able to be displayed on the map.
Would it be possible for you to post your data so we can take a look? If you go to File > Create Map Package, you can make a .mpk that contains both the feature class in a file geodatabase and its map document.
Alternatively, you can contact Esri Support so an analyst can work with you directly on this.
