Very good point. In the past, I have suffered by buying smaller high growth high margin company in the large group, only to find it getting merged in large slow moving low margin(relatively speaking) company and thereby destroying shareholder value for the minority shareholders of the smaller entity. For eg. Astec merging in Godrej Agrovet.
Hence I decided to stay away from companies like Tata Metaliks (possible merger in Tata Steel), Tata Elxsi ( TCS) etc. I am sure there would be many more companies falling in this category…