As I mentioned in my last post, the Battle Mastery system of the Super Robot Wars games deserves some recognition, so I will write a bit more about it today.
In the Super Robot Wars Original Generation games, every battle has an optional victory condition called the Battle Mastery condition. This condition has no bearing on the battle itself, but every Battle Mastery you acquire adds to the difficulty of the game; if you get no Battle Masteries, you will be on the Easy difficulty, but if you get many you will be on Hard difficulty, where you will earn less money and experience while fighting stronger foes. Other than the difficulty setting, fulfilling Battle Mastery conditions has a few more effects: some Battle Mastery objectives are tied to unlocking hidden items and units, and, more importantly, you can only play the final mission of the game and fight the true final boss if you have completed a sufficiently large number of Battle Mastery conditions (in SRW:OG2, most sources say that you can only miss three out of 41 and still reach the final mission).
I think the way this system controls difficulty is brilliantly elegant. If a player is inclined to take on optional challenges (in other words, the kind of person who likes to play videogames for the challenge), then the game becomes more difficult to match. On the other hand, a person who just wants to play through the game for the story is not compelled to take on the challenge of the Battle Masteries and is allowed to play through on an easier route. What is more, the difficulty level scales gradually, so to a certain degree the player can adjust the difficult to a comfortable level by simply earning Battle Masteries where he can and ignoring the ones he can't. It is a system which is fair to all kinds of players and controls the difficulty without an awkward difficulty selection choice (well, there is one, but that is only for unlockable extremely hard and extremely easy versions, which also scale). I can't state enough how much I like the concept of this system.
Praise aside, there is one problem I do have with the Battle Mastery system as it is seen in SRW:OG and OG2. The main reward for having a lot of Battle Masteries is being able to see the true final battle, a dramatic and fun finale that is an important conclusion to the plot. If you do not have enough Battle Masteries, there is a sudden and unsatisfying interruption in the flow of events that leads to a hasty ending. What is more, the true final battle of OG1 (which I missed originally) is assumed as the real series of events in the following game, which can result in confusion for people playing the sequel who did not see it (like me). Forcing a player who wants to see the dramatic finale to play through the most difficult route through the game is a flawed concept, in my opinion. It is just a better experience for the player if he can see the whole game as it is meant to be seen, regardless of difficulty.
Despite that one objection, I do like the idea of having rewards for players who are willing to take on a challenge. Certainly, it would be a good idea to link hidden units and items to the Battle Mastery system. At least, I would prefer to do that than use the esoteric conditions so often seen in the SRW series. Another possibility would be to tie Battle Masteries to unlockable game modes, minigames, glossaries (SRW:OG2 could really use a character/mech glossary), or other similar things.
I should also discuss the actual conditions used in the battles... As a whole, almost any condition for earning a Battle Mastery works well, so long as it is more difficult than just completing the normal mission while still remaining possible. I prefer Battle Mastery conditions that can be cleared in the early stage of a mission, rather than ones which enforce a time-limit on a whole battle (mostly because the latter make it hard to build up weaker characters), but that is just a preference. The only Battle Masteries that I think are poorly designed are the ones that must be achieved through relying on luck or the AI moving right rather than player preparation and strategy (such as OG2's Mission 16 or Mission 20 on the Aviano route). The latter, which tend to be things like protecting weak allies or killing enemies timeframe that is so limited that you must rely on the enemies moving in a specific manner, are simply frustrating and are not a good measure of the player's skill level, so they are not fun and not a good way to determine challenge level.
Anyways, I think the Battle Mastery system is a good concept that could easily be implemented in other games. Games have been offering optional challenges linked at least since Goldeneye for the N64, and many other games (like the Devil May Cry series) rate the player based on ability. A system like the one in Super Robot Wars would fit games like those very well.