I find myself frustrated that Wizards have high incentive to invest in Dexterity and Constitution so that the aren't quite so squishy whereas they have little incentive to increase Wisdom except to help their Wisdom saves. Wisdom, however, seems much more in line with the common imaginings of a Wizard than Dexterity.
I am considering house-ruling that wizards can choose to add their Wisdom modifier to their AC instead of Dexterity but I want to check whether that would be balanced. Essentially any time AC is mentioned they could substitute WIS instead. Without mage armor they could have 10 + WIS, with mage armor they could have 13 + WIS. I don't think I would allow a multiclass to use this.
A lore justification for this would be their arcane studies have caused them to subconsciously weave magic around themselves making them more difficult to hit.
A relevant aspect to this change is that wizards have Wisdom Saving throw proficiency so this would allow them to be really good at Wisdom Saving throws more easily. On the other hand Dexterity saving throws are also quite common so giving up points in Dex also has a high cost even without AC.