One thing that I eludes me - I'm not that bright - is whether the Wizard spells are cast with CHA or INT. But you can dump-stat INT and then use the Ogre Circlet of Intelligence (17 INT).
Wizard spells use INT and Wizard's number of spell slots are based on their INT
Which can make Wiz multiclasses a little awkward.
Either you go heavy CHR + INT at the cost of other stats (Like CON and DEX), lock yourself to the Headband of Intelligence (Setting you to 17 INT which means only a +3 modifier) or resign yourself to a handful of non-stat scaled spells learned using the Wizard class (Such as ritual spells like Longstrider, Feather Fall, Enhance Leap or utility spells like Shield, Knock, Misty Step, Mage Armour etc)
These methods can certainly all work, but you need to have a good idea of why you're jumping through these hoops when you could simply play a Sorcerer, Bard or Wizard as is (Or using some other potent multiclasses like SorLock, BardLock, Arcane Trickzard, Eldritch Knizard - All of which utilize the same casting stats between their classes)
