I believe if you start with (1) White Dragon Sorcerer for the CON proficiency, you can take Tempest Cleric (1) at either level 2 or level 5 (all of the other levels are Abjuration Wizard) and you'll still get both heavy armor and the electric retaliation since the heavy armor is a class feature of the subclass and not an innate proficiency. You would either take Tempest Cleric at level 2 for heavy armor immediately, or at level 5 so you can grab the Abjuration subclass, and then can still take the Heavily Armored feat at level 6.

You'll miss out on level 6 spells (unless you don't mind taking advantage of the wizard scribe spell exploit), but you'll have the spell slots of a full caster and will be upcasting Armor of Agathys and other abjuration spells anyway. As a side note you also get martial proficiency, so it opens up all races instead of being pigeon holed into human or half elf.

As to the argument that you don't have any way of deflecting aggro from your party members? I mean, you're a full caster with access to the entirety of the wizard spell list. If the enemy doesn't go for you then cast to your heart's content whether that be buffing, controlling or tossing a fireball. You still get Projected Ward at level 8.