First of all, an observation: in my experience, multi-class wizards (and, to a lesser degree, clerics) suck; you wind up with a character who's dramatically inferior at everything. The following is a sudden idea I had for making multiclass spellcasters playable, but hopefully without being unreasonable:
Feat: Improved Spellcasting
Prerequisite: multi-class spellcaster
Increases your spellcaster level by 1 (in one subclass, if multiple types of spellcaster) for purposes of spells known and effects of spells (i.e. same as the PrC '+1 level to existing class' ability). May be taken multiple times, with the following restrictions:
1) Spellcaster level must always be lower than character level (note: this means the feat cannot be taken at first level).
2) You may not take this feat more times than the actual number of class levels you have.
Now, I admit that +1 caster level is, in general, way overpowered for a feat -- but it seems like it might be a fair way to balance out something that's otherwise really discouraged.
Thus, a 10th level character (Ftr5/Wiz5) might take this feat three times, in which case he casts spells as an 8th level wizard, has an attack bonus of +7 (roughly equivalent to a 7th level fighter), and, assuming a +2 con bonus, probably has 64 hp, equivalent to an 8th level fighter.
Feat: Improved Spellcasting
Prerequisite: multi-class spellcaster
Increases your spellcaster level by 1 (in one subclass, if multiple types of spellcaster) for purposes of spells known and effects of spells (i.e. same as the PrC '+1 level to existing class' ability). May be taken multiple times, with the following restrictions:
1) Spellcaster level must always be lower than character level (note: this means the feat cannot be taken at first level).
2) You may not take this feat more times than the actual number of class levels you have.
Now, I admit that +1 caster level is, in general, way overpowered for a feat -- but it seems like it might be a fair way to balance out something that's otherwise really discouraged.
Thus, a 10th level character (Ftr5/Wiz5) might take this feat three times, in which case he casts spells as an 8th level wizard, has an attack bonus of +7 (roughly equivalent to a 7th level fighter), and, assuming a +2 con bonus, probably has 64 hp, equivalent to an 8th level fighter.