paladin - you get immunity to fear, huge boost for saving throws and access to heavy armor and tower shield which will allow you to play like armored sorcerer with (automatic) still spell metamagic
blackguard - evil alternative of paladin for evil sorcerers
pale master - immunity to critical hit and sneak attack, ac bonus, immunity to stun, unlike wizard it wont give you new spell levels but if you have community patch you can toggle a rule switch in PC Widget which will give you caster level bonus for palemaster levels
rogue (or bard if you prefer from roleplay reasons) - rogue skills are always good
red dragon disciple - it adds charisma and constitution and ac so even if you want remain caster and not play like spellsword style its a possibility to consider