GlassJaw
Hero
So I was kind of hoping that we could use Bound to actually keep our core numbers up, as it seems intended to do, despite the fact that we're getting expensive but non-useful treasure.
Ahh, gotcha. Well those are some pretty sweet items but I see your point. Further increasing the "+" of those items is technically increasing their value beyond what you would normally have otherwise.
You could ask your DM to allow Bound Item to "convert" the properties into their equivalent numeric enhancement bonus. I would certainly allow that.
Heck, I'd even allow you to change it on the fly (or with a Standard Action maybe). It's like the Bound Item ability is giving you "control" over the item's magic properties.
I quite like that in fact. It's not giving the player something more powerful than they already have yet it gives the player flexibility to use items they find, further reducing the reliance on crafting items.