Honestly, I don't think I would care much for an introduction of a third type.
Note that this post is NOT addressing the games as a whole, and is focused on the battle mechanics of the games.
Speaking from the standpoint of a competitive battler, the battle system of Pokémon is unique. The sheer amount of depth and strategy you find in all aspects of battling - choosing the Pokés for your team, choosing the correct movesets for your Pokés based on the options given to you while making sure to keep opposing strategies in mind, making difficult decisions, and having it turn out alright is a feeling like no other. It's as close to perfect as can be. That's not to say there's no luck involved - there's a lot of luck, in fact, but the fact that so many people can still manage to play it and enjoy it so well despite that luck is a testament to how great the system is.
Adding in a third type would change all of this. There's no guarantee that a three-type system would be at all balanced - yes, I know there are tiers, and there are types that are slightly favored, but there's no one type that has a monopoly on the game. And with three types, there's no telling what could happen. It could screw up the tiering system completely - up until now, power has never been too much of an issue, what with the current organization of tiers based on usage. With three types though, the new immunities and weaknesses would be insane. One move could automatically be a OHKO on certain Pokemon due to being 8x effective. Say that Pokemon has some of the best of the best stats, though, and is moved to a lower tier due to it dying to one of the more popular types. Then, where does it go? It might not fit the lower tiers based on power, it won't fit in the higher tiers based on usage - where does that leave the tiering system? The whole point of the system now is to make sure every Pokemon has its own use - if it's not as viable in the upper tiers, that usually means it's a perfect fit for a lower one. Not anymore.
With the addition of types - how are move powers calculated? Will they have to change currently existing mechanics, and if this happens does the competitive scene have to start over in terms of strategy and even investigating the mechanics and building simulators?
Does this mean existing Pokemon would be changed to fit the new three-type norm? Would they not be changed and be left behind in this "revolution" of sorts?
Will this game still cater to all audiences?
Okay, honestly I'm not so sure where I'm going with this post anymore. I had an idea at first, and it sort of faded as I was writing this. Ended up rambling a LOT. I know there are other reasons, I just can't think straight right now.
suffice it to say that I'm not the biggest fan of a third type. [/mindless, thoughtless rant]
Edited by ovarloard, 06 November 2011 - 06:38 PM.