The big advantage to alchemy is it doesn't interfere with dual-wielding
The big downside is qty of potions.
If you never fast-travel and walk everywhere... you could pick up enough ingredients that alchemy would be viable consistently and regularly. If you fast travel, you'll prolly have to try and buy up ingredients....
You can also get magic enchantments on your gear to assist with magic damage resistance.
And while yes... alteration has some deep perk requirements... it could also be well worth it. He can skip Mage aromor out of hand (he uses light) and dual-casting isn't really required either.
That leaves 5 if he wants to go all the way to Master, 3 for Magic Resistence, 1 for Atronach, and 1 for Stability. And you don't even need all of that even. Adept level is only 3 perks, and would allow him to boost his armor rating by 80 on demand. That would allow him Stability (so a single 1 hand cast lasts full duration of most fights) and Magic Resistance (30%) for 7 perks in total. (counting the cost reduc perks).
That's not too shabby for a 7 perk investment.
Alternatively... he could skip Magic Resistance and gun straight for Atronach which is like 30% dmg reduc on it's own. Take up to Expert (4 perks) allowing EbonyFlesh to boost his armor by 100 on demand (when needed) stability is worth 1 perk since he's there, and Atronach is only 1 perk for a total of 6. The downside here of course is that he'd have to get it to 100 before seeing magic reduc. Trasmute and Telekinesis makes that relatively easy though.
Speaking of..,.. someone mentioned a trick of using Telekinesis to throw a necklace/valuable between bandits who would then fight each other over the item. Haven't tried it but I've been meaning to....