ok sir. you did forget the thahd in the clearing as well as the large roamer you find in the back of a bandit stronghold. Also Alpha Hyrk in the shaper hermit dudes cave in BArzite Lands. There are a few flaws to your ideas.
These creations that you pick up have been independant for who knows how long. They are also creations that you did not create. These two facts give me the impression that we shouldnt be able to shape them into stronger beings, which is really what we are doing when we upgrade our creations stats, and to control them in battle. Also, I believe that alone the rat and the vlish both do poorly on the battlefield, and the Alpha doesnt last very long depending on what stage of the game you pick him up in.
I agree that the recruitment thing was big in this game and I found Heust Blade, the Roamer, and the Alpha to be effective fighters. I just think that since they are not your creations you shouldnt be able to control them like other games.