I wouldn't be annoyed if someone wanted to, e.g., enchant a Tentacle Whip with various weapon enchantments. That makes perfect sense to me. It is, in part at least, a weapon. Hell, I'd also probably not be all that annoyed if someone wanted to ask for ways to beef up symbionts since they are not all that well supported and have a nice "price these like magic items" limiting logic to them. And, the idea that they are living equipment also seems sensible, although they don't suck up slots, so that should be taken into account.
However, Captnq's quote doesn't imply what he says it does. It's very dodgy to cite that as if it's a justification. By that logic, you could enchant a magic item location -- it "enhances your character's abilities in much the same way as a magic item does" and it's "power level is measured in gold pieces." You just let me know when you get a +3 Vorpal Frog God's Fane up and running ...