Isn't muscle wizard just monk? I CAST KI STRIKE
3.5 does have the
Rage Mage prestige class in Complete Warrior, for multiclass barbarian/spellcasters. It's basically what it sounds like, you get to cast spells while in a rage. Of course, that's oversimplifying.
Cons (no pun intended): Half spell progression, requires 4BAB and rage (or frenzy, gwaHAHAHA). Obviously doesn't match the strengths of a pure barbarian or pure spellcaster.
Pros:
Uses character level for most spells in a rage, mitigating the half spell progression.
Eventually gets a +2/+4 bonus to save DC on top of that
-10% to arcane spell failure chance at 2nd level. This gives a mithral chain shirt no ASF.
The capstone is pretty funny
The loss of high level spells basically trumps everything, but I still think it sounds fun for a hybrid character. The save DCs are a bit higher than a pure spellcaster, which is nice, and it'll be easier to land spells due to 2/3 BAB.
Spells per day will suffer, but I think wands/scrolls would work fine in the spell rage. Simply attacking with a weapon is also an option.
GiantITP hates it of course, offering much better "gishes" which involve 5 different classes and obscure books
They assume it'd be barbarian/sorcerer, or "mystic ranger" for some cheese I don't get. It's a shame that using cleric would waste almost all the benefits, heh.
Tempted to plan up an alienist combo just for the "raving lunatic" lulz.
Yeah, no magic class adds Con to anything other than bonus spells per day, at least from 3.x edition. There's the Tome of Battle Swordsage which uses martial maneuvers that work kinda like spells, and Insightful Strike adds your Concentration check (which is Con based) instead of your normal modifiers to the melee attack. There's also a bunch of ways to get Con to AC and Reflex/Will saves too.
The CON replacements on the great
X To Y thread are pretty limited or defense-oriented for all classes. Probably because it's such a vital stat for any character's survivability. Even "single attribute dependent" classes like most spellcasters need CON, arguably more than DEX. Making it a spellcasting stat would be... hard to balance.