Myrrh, Frankincense, and Steel: Kurald Galain's Guide to the Magus

[Kurald Galain]

I don't think Kensai really favors Str or Dex, it depends on the weapon you pick up. I suppose you can get into Slashing Grace or Fencing Grace at 1st level but that's really the only difference compared to regular Magus.

Indeed. However, note that Slashing Grace was errata'ed to no longer work with spell combat.

...not that I would recommend a kensai at level one, though.

Canny Defense doesn't work with anything heavier than light armor.

Kensai aren't proficient in armor at all. However, a strength-based Kensai could simply use his defensive buff spells to compensate for his lower armor class. Also, using a wand or Spell Blending to get Mage Armor is a decent trick.