I might be worried about is the capstone. While this ability isn't severely overpowered, it does have enough that some DMs might nerf it (or simply not allow the class).
My biggest issue is with spell resistance. I think it defeats the purpose of the class and conflicts with the style of it. I sort of can see the circuit mage being bombarded with spells and gaining benefits in turn for taking damage. If he immune to many of these effects it just... Well, I think in this circumstance spell resistance raises this class an entire tier on its own.
Still I like the massive flexibility of this class and how the system you have set up interplays with itself is amazing.