Imagine if you couldn't change your choice
Now let's play the version of RPS that many games with open world PvP ask you to play: Everyone declares themselves rock, paper, or scissors, and then they're stuck with that choice forever.
Imagine your office was an ongoing game of RPS where everyone is forced to choose one move and then play that every time, even when it will make them lose:
Everybody gathers around to pick out some fabric and patterns and thread out of a box. You need to sew yourself a shirt with an R, P, or S on it, and wear it every day as part of your uniform. Now every time you pass one of your coworkers in the hall, see who wins!
In the meantime until you finish sewing the shirt, you're a "lowbie" who just automatically loses to everyone who's finished making theirs. After a week or so, you've finished your special shirt with an S on it. It looks great on you. You come to work, excited to finally have a chance at winning.
Unfortunately for you, your office has a lot of R shirts, and they always trumps your S. I pass you in the kitchen: you lose! Later you pass the IT guy on the stairs: you lose! At lunchtime you meet up with some friends: you lose! It seems that everyone picked R, and there's nobody around you can win against. How were you supposed to know everyone would pick R?
In the parking lot, you spot Bob, who's a P. All right, you finally win one, but Bob doesn't really care, because he's the one who wins against all the other R jerks in the office. Frustrated, you decide you should throw away your S shirt and start sewing a P shirt, so you can be like Bob and start winning for once.
After a week of working around the clock to sew your new P shirt (and losing the whole time), you finally have a shirt with a P on it like your frien Bob. You rush to work, excited. But wait, what? When you read your email, you see that the rules have changed and now the order has switched. All the Rs you were hoping to win against today now win against YOU! If you would have stayed an R, you'd have beaten all these guys, but now you lose even more than last week, because of a change you couldn't see coming.
This is how it feels every time someone levels up an MMO character, only to realize that the rock to their scissors is actually the most played class in the game. Or that the only that their class is good at killing turns out to have just been nerfed to the point of unpopularity. Or that the group they were supposed to be able to win against can now easily beat them, due to a rule change or patch.
It's especially bad in games with open "world" PvP, where you can be attacked by anyone at any time. While you're leveling up your character, any high level character can come by and stomp you, and by the time you're finally done you may be stuck constantly losing because of who happens to be playing the game as a given class on that game/server/day. Do you really have the patience to sew yourself another new shirt, or do you want to quit this game?
Ok, Let's try chess
You be a rook and I'll be a bishop. I'm very dangerous if you stand at an angle to me, and you're lethal to me if I stand straight on. We take turns moving, until one of us tricks the other into standing in the wrong spot, and wins. Now Bob shows up, and he's a Knight.
Which piece beats which, in a game of Rook, Bishop, Knight? Well, I guess nobody can tell for sure, because it's all a question of getting the other person into a situation where they're exposed to your killing blow. The knight is more versatile, but has shorter range. The bishop and rook have blind spots, but unlimited movement. [Pawns, queens, and kings would definitely not be balanced, which is why I'm leaving them out]
We all take turns dueling. This is more fun than the tshirts, but it's a little too easy to avoid danger once you learn the other person's abilities. The game is TOO balanced! [Actually, the way players tend to think, we'd be more likely to each complain about each other being "too hard to kill." Usually the only time a player thinks their class is balanced is when it's overpowered.]
Let's add a resource to spend. Every 5 turns, I can declare that you're snared, which makes your next move shorter. Now we've got to avoid danger, but also think one move ahead, and make sure that we're not going to be snared in a spot that gets us killed. Now if I know you've just used up your snare, I can play more aggressively for 4 turns. Let's add a die roll, so there's a 1/6 chance of a snare missing. We're on our way to a fun game that emphasizes our choices, not our classes.
Now for some Team Fortress 2
It's our first day of TF2. You decide to learn sniper, and I decide to learn pyro. We play 10 games of 1 on 1 deathmatch. Hrm, what do people see in this game? Whenever we're in an open field, you can easily snipe me, and whenever we're in a hallway, I roast you. Eventually you just start waiting for me in the open field, and I start waiting for you in the hallway. We're bored.
Oops, what button did I just hit? I'm a spy now? Hey, I can be invisible. I sneak out of the hallway and around the open field. I come up behind you and stab you in the back. Take that!
Now we start picking lots of new classes every time we die, and we start to learn about the game. If I kill your sniper in a hallway with a flamethrower, you come back as a demoman and bounce a few grenades into that hallway. You snipe me, so I come back as a double-jumping scout who's hard to shoot and is good at closing distance.
This is actually a lot like Rock, Paper, Scissors, except sometimes paper gets a lucky shot on scissors, and gets to do some gloating. Bob's online now, so we join his game. He's in a game full of all kinds of players playing team deathmatch. The enemy team has too many medics healing people, so our team all starts playing pyro to roast them. Oops, now their team is all engineers, and they're mowing us down. We send a few people in as spies, and then someone decides to play sniper to cover that open field. Even without a plan, the team begins to organically identify and fill needed roles.
Now the map switches to something with an objective, like capture the flag. We know there are a bunch of pyros in that hallway, but we have to get in there to complete our objective. Bob stays behind to play defense as engineer, while I go medic to heal you as a heavy.
Once the game gets into full swing, we've all got some interesting choices to make. The team balance calls for a sniper right now, but I'm not very good at it. Should I stay a class that I can play, that might not be as useful right now, or take my chances with sniping, because it could help my team win? I'm going to play this game every day, until I'm good at ALL the classes.
Supply and demand
Just like the tshirt example, TF2 involves people rushing over to the side that they think will be most powerful in a given scenario. Except they can turn on a dime. It takes 20 or so seconds to come back as a different class. If your entire team decides to become scouts to get past the snipers, it's a juicy opportunity for just one player to go pyro and wipe the whole pack of you out.
In this way, the maps and classes balance themselves. The more engineers there are, the more powerful spies become. But if you guess that the engineers will be expecting a spy, you can take a chance with a demoman or medic, which isn't as devastating but isn't what they'll be preparing for. If you think a few moves ahead of the enemy, you can trick them into walking into a trap. In this game, like our game with the chess pieces, what you do and who you are both matter. Choosing the right role at the right time can make up for a skill deficit, but the "wrong" class can win the day if it's played with enough skill.
Games to watch
There are several games, mostly shooters, that let you switch who you are and what you can do. Several of the Battlefield games let you pick up a weapon pack from a different class's corpse, and continue playing with their abilities. Team Fortress and Natural Selection allow you to switch very often, around once per life. Counterstrike lets you buy new weapons each round, as well as pick up other weapons instantly off the ground.
Planetside and Eve Online are MMOs that allow the player to build up training in lots of different areas, and then choose which ship or powers to use. Choosing roles happens less often in these games, generally requiring a visit to a hanger or a factory. It sounds like The Agency will allow players to swap out their powers by changing the equipment they're wearing. I'm looking forward to seeing this in action.
There's definitely a place for Rock, Paper, Scissors game design, but I think the stronger those trumping abilities are, the easier it needs to be to switch between Rock and Paper at a moment's notice. I like playing a single class in MMOs for hundreds of hours, but I want to know that my tactics and strategy will be able to win fights for me. I don't want to be left frustrated after a fight, wishing I'd have rolled a different class so I wouldn't have to lose so much.