Multiclassing

[Hey_I_Can_Chan]

Every time you don't gain a point of Base Attack Bonus in a class that isn't a full caster, you gain +1 to your spellcasting level.

Elegant and easy.

[erik]

Every time you don't gain a point of Base Attack Bonus in a class that isn't a full caster, you gain +1 to your spellcasting level.

Elegant and easy.

But that doesn't fix anything. If you continue to get +1 BAB and no caster level then you suck as a caster. If you continue to get +1 caster level and no BAB then you suck as a fighter.

I like the idea, similar to Iaimeki's prestige class (or maybe it's exactly what Iaimeki had in mind, I never saw the nitty gritty), of simply having a amalgam class that you can put levels into and add to any other class you have taken levels in. For anything duplicated like skill points or hit die, use the highest. Obviously in such a case, nobody would ever take level 2 of any class.

[JonSetanta]

Hitting and causing spellcasting effects are very different things.

If anything, BAB should be an ability one can grab that says "Your attack roll bonus is equal to your class level", showing clearly how much warriors lack further benefits in all the other 19+ levels.

If the 'AB = level' ability was part of a chain such as, say, 1/2 level -> 3/4 level -> equal to level that might work better.