What, you have Mirrodin but no Memnarch? Blasphemy!

The plates all look nice, though I think adamantine plate should give an AC bonus (You should look at the warforged plates from Races of Eberron to get some inspiration. In fact, if you do make this an inherited template, these plates would work a lot better as feats instead of templates)

Your example human should have a bonus feat.

I feel like this should turn them into constructs. You know? Not just metal humanoids. Robot humanoids. Or robot dire lions. Yeah, that's what I'm talking about!

Let's see...your mirran template does feel a little weak for LA +1, but not by much. Another small boon should do it. Oh, how about SR? SR 5+HD. That's a nice little boost (I have no idea if it fits with the Scars of Mirrodin lore, but metallic skin = reflect spells).