Skyrim talk:Spell Absorption - UESPWiki
According to this, one person had 92.5 absorption, but he picked the Atronach perk before he was a vampire. So if you become a vampire, select the Necromage perk, then activate the Atronach stone and pick the Atronach perk after, you should have 100%, someone else from the link said he was standing in a flamethrower trap for 5 minutes unhurt, unaffected by all spells so far, and after he cured vampirism he retained 100% spell absorb.
When I said immune I thought that was still acceptable because if you are 100% absorb you don't take any damage from magic, so you are technically immune to it. But I see what you mean it sounds like resistance, my mistake for not providing all the sources and such up front. I ended up making it confusing for lots of people. I'm new to the forum so I am still trying to learn how to behave properly.
Edit: I guess since I'm the one who originally brought up this preposterous idea, I should probably go ahead and test it. The earliest I can do that is tomorrow, lets say about 30 hours from now I should be able to get on and test and post an answer.