Well one thing is that there code is based on php 4 when it comes to the contructor as they use the objects name instead of __construct() php 4 is really really old and php is no longer updating it so i would not go that way.
Also, in codeigniter, at least as far as i can tell, there base model class provide basrely any functionality, like functionality to save, load data, queries for multiple records all of which can be abstract so that is is the same for all models. If you don't want to(or can't) build something like that i would suggestion integrating a ORM system.