Economies of Scope
This is a similar concept to that of economies of scale. The principal difference is that economies of scope involve the variety instead of the quantity of elements. In other words, there is an economy of scope if additional elements are continuously more useful the more you diversify.
Typical examples can be seen in strategy games where it is useful to have armies that make use of combined arms (infantry units supported by tanks and artillery). (Rollings and Morris 2000). Other examples can be seen in games such as RPGs where characters with different abilities complement each other.
A diseconomy of scope is when the opposite happens. For example, in many strategy games, groups of units move at the speed of the slowest element in them. In this case, fast units are less useful because they are in the same group as slow ones.
In Pokemon it is advantageous to use several different types of pokemon so as not to have several weaknesses to a single type. However, some types of pokemon are weaker than others and your party is limited to six so only a certain amount of diversity can be attained.
Civ IV is a strong example because of the fact that in order to win a player has to take into account many different aspects of the game and find the balance between them. Players need to be able to make money, manage population, raise an army, research technologies, and be diplomic. Also the combat system is such that you want to have a balanced force, being that for every unit there is a counter. and not only do you want a balanced force but you need to balance its size, because there are some units that will do damage to every unit on a stack and not just the one that fights.
Tales of Symphonia
Tales of Symphonia displays a strong economy of scope because each of the fighters within the game in your party at one time each have a unique fighting style. In order to defeat any number of enemies, a certain combination of your party members would be most advantageous to fight specific monsters. For example, multiple characters can use magic, but each character uses a different type of magic, and so to have each character would be to be able to exploit any magic weakness in any enemy. Of the characters that do not use magic, they each have a unique fighting style; one character uses a sword with magic, another uses two swords for quick damage, one uses a gigantic axe for slow but massive damage, and the last character uses his feet for quick combo attacks. Each of these fighters employ very different fighting styles, but as the person playing the game can only have four players per fight, they must pick which of the eight are the best four suited to their current needs. But, overall, having all eight fighting styles within one's party insures that the player will be able to overcome any type of enemy he or she comes across.
StarCraft for the PC is a classic example of an economy of scope. There is great benefit to having diverse and balanced resources. Since the world is one of incomplete information, it's often very useful to be prepared for anything. This is why it is valuable to have units to protect against ground, air, mass, cloaking, etc. Dominant strategies require a variety of the infantry, healers, resource gatherers, spell casters, and siege units. Most entities complement each other in such a way that if you are lacking any of them, then you have a distinct weakness. In particular, players could take advantage of economies of scope by fielding groups with mixed abilities: for example 8 infantry (good at ranged combat) and 4 firebats (good at close quarters combat) instead of 12 plain infantry. In the expansion, which added medics, it was common to add a few to an existing group so that the medics would automatically heal the wounded members of the group while receiving protection from the soldiers.
Rollings, A. and D. Morris (2000). Game Architecture and Design. Scottsdale, Arizona, Coriolis.