Looks quite reasonable to me. In fact I'd be inclined to not even require the feat tax to do this in my game- if the caster has already spent the feats to be able to craft Constructs of his own (and IME, very few PCs do), then doing cool stuff like that should be allowed for much the same reason creating Cool Grimoires doesn't require much in the way of crafting ability (see the examples in chapter 2 of Ultimate Magic).