You don't need the CMA&A feat or the armor slot to craft Bracers of Armor.
I've got no problem with someone building Bracers of Armor into shirt form with the CWI feat, the Mage Armor spell, and a CL at least twice the bonus, with a 1.5x inaffinity cost.
Whether or not they're allowed to add armor special abilities would depend on whether the DM was using the Arms and Equipment Guide, with its otherwise nonexistent rule that Bracers can contain special abilities.
You're not making the shirt into magic armor with a +X enhancement bonus to a +0 armor bonus; you're making the shirt into a wondrous item that surrounds the wearer with an invisible but tangible field of force, granting him an armor bonus of +1 to +8, just as though he were wearing armor.
-Hyp.