-The character concept revolves around draconic feats as well as metamagic feats. Replacing those with 'life saving' feats breaks the concept.
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-Wearing armor isn't really going to improve things. I've already got an AC of 18 (using mage armour) or 20 (using greater mage armour) increased to 22 or 24 with shield.
Seriously- reexamine armor, given your concept.
The Draconic Feats chain has 3 feats that will help your survivability: Draconic Skin gives you +1NAC. Draconic Armor (from Draconomicon) gets you a round of DR based on the level of the spell you just cast. Draconic Breath makes being an effective armored mage viable by letting you maintain distance from your foe and avoiding ASF penalties by letting you deliver a magical AE attack (cone or line) doing 2d6/spell level per affected space.
My Mage Brute had an AC of 19- Scale + Lg Shield + 16Dex- all without expending a spell slot. No worries about the time it takes to cast your buffs; no worries about provoking AoOs casting the buffs; no worries about spells getting disrupted, dispelled or simply expiring. And once he had the GP to spend, he could get masterwork- or better yet, Mithril- armor that he could then enchant with further protective energies. (The campaign ended before then due to real world issues.)
Add to that:
1) Still Spell lets you maintain most of your spell arsenal at your now-armored fingertips
2) Dragon #354 has a (flawed) list of arcane spells in the PHB and Spell Compendium that don't have somatic components.
3) Learn Reduce Person and it will get you another +2AC boost without affecting your effectiveness.
4) You're hiding in plain sight- most NPCs won't pick out the guy in heavy armor as an Arcanist and won't react to him as such...especially if he's not waving his hands about like a spellcaster. A good reason to have your crossbow handy.