dnd 5e – Would allowing a character to gain bonuses for two shields be unbalanced? (D&D 5e)

I have a character I’ve been working on who worships a god of protection. The idea is that he will use two shields, but the handbook states you can only gain a bonus from one. Obviously the character will be severely limited in terms of damage output (improvised/unarmed attacks (kicks) only). My question is–will the increase in Armor Class (AC at first level with chainmail will be 20) Overcome the limited attack bonuses and damage output of this character? I plan to optimize at later levels with thing like the sentinel feat to make this character able to protect the squishies.