Hmmm I understand all of your concerns about the first gym being easy, but you have to think that they made your rival pick the opposite pokemon so it would be a "challenge" to you everytime you battle him/her.
I have an idea that I came up with while typing what I said above: How about the first gym change according to what pokemon type you chose. So Grass would have a Flying gym, Water would have an Electric gym, and Fire would have a Rock gym.
One great thing about opposites are this: It forces you to catch other pokemon to find a weaknes. For example, whenever I choose charmander for FR/LG, I usually capture a Caterpie (to evolve into a Butterfree for his Confusion attack) or a Mankey (for it's Karate Chop). Sure Butterfree is a bug/flying pokemon (a double negative against a rock pokemon), but I like to think "Hit 'em hard, and hit 'em fast" when it comes to that battle.
I believe every game has at least pokemon to help win a battle. Just take a look at the first three in FR/LG:
Brock: Starter, Butterfree, or Mankey
Missy: Starter, Pikachu, Bellsprout
Lt Surge: Diglet/Dugtrio, Geodude, NidoKing.