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We created quite a few houserules for sorcerer's. They are strong, but a well-played wizard still outshines a sorcerer. This is the main reason we house-ruled sorcerer's, so they would be more entertaining to play.
Sorcerer's gain bonus feats in our campaign:
1st level: Eschew Materials (Gave this to them almost immediately after the Tome of Blood hit the shelves. Fits perfectly for a sorcerer.)
It is still easier to cast spells with components, but in a pinch a sorcerer can still cast any of their low cost component spells as a full round action per the usual rules for metamagic.
Bonus feat at 5th, 10th, 15th and 20th: We gave sorcerers bonus feats every 5 levels just like wizards.
They may choose from the following list: Any metamagic feat, spell focus, spell penetration, arcane preparation or extra spell known.
In my opinion, sorcerer's are not wizard warriors or pseudo-wizards. Sorcerer's are a class who can innately channel magic. They love magic just as much as a wizard and spend their lives trying to master it and channel it as effectively as possible.
Thus, sorcerer's gain bonus feats because of the immense amount of time they spend learning to channel the magic they do know. They do not gain item creation feats, because they do not care about making items that harness magic. There primary concern is learning the secrets of metamagic or focusing on certain types of magic such as ecovation or enchantment to improve the power of their personal magic.
Sorcerer's are the ultmate channelers of magical energy. Magic is an art to them and not a science as it is to wizards. In my opinion, sorcerer's should be better at mastering metamagic and the spells they do know should be more powerful than a wizards. This is the reason for the varied bonus feat list.
Bonus spells known for High Intelligence Sorcerer's gain bonus spells known based on their intelligence. I felt that a more intelligent sorcerer's would be able to learn more spells than a less intelligent sorcerer.
In average campaigns, this is likely to give a sorcerer an extra 1st or 2nd level spell, while at the same time taking a fairly high stat from dex, con, str, or wisdom. I felt that this was a balancing factor in the choice to allow a sorcerer to know more spells than normal.
In the long term, a sorcerer who obtains magical items to boost their intelligence will be more powerful, but still nowhere near as versatile as a wizard. I have not noticed any imbalance in power in favor of the sorcerer as of yet in any of my campaigns because of this rule.
I am also currently working on a rule to allow sorcerer's to unlearn spells in favor of different spells at a later time. It can't be an easy process to ensure that it is not done often, but it shouldn't be impossible either. They should have put some means of changing spell slots in the actual game rather. It seems rather unreal that a sorcerer can't given time change out a spell slot.
I made the above changes to make the sorcerer a more interesting character class with more customizable features. I feel the above houserules allow a person to make varied sorcerer's without all of them being combat mongers. For example, instead of making a combat monger sorcerer, you could make a buffing sorcerer. Load up with spells that buff other players like haste, greater magic weapon, the various ability increasing spells, fly, and other such spells. Supplement these abilities with metamagic feats such as extend spell, persistent spell, and chain spell, and you have a great buffing sorcerer.
Even with the above changes, I feel the wizard is still a far more viable class for anything less than inflicing mass destruction upon enemies, which wizards are none to shabby at either. At the current time, I play one sorcerer and two wizards. The sorcerer has more firepower than my wizards, but my wizards would win in a duel and are more helpful to the adventuring party. Their versatility makes up for the lesser number of spell slots and the lack of spontaneous casting.
Anyway, those are the houserules we use for the sorcerer. They have not to date proven to imbalance our campaign. The only effect they have had so far is to make the sorcerer a more viable and customizable class.