So I read the sutra excerpts that you posted, and I am a bit confused as to why you brought up the emptiness of unconditioned things versus the emptiness of conditioned things in response to Queequeg. One says "If one is diligent in the emptiness of compounded and uncompounded phenomena, one is called 'diligent.'" Both the conditioned and unconditioned are empty. Another says, "That being the case, child of a good family, the Buddha is the the dharma, the dharma is the sangha. The sangha is uncompounded. The uncompounded is emptiness. The emptiness of the uncompounded, the emptiness of the compounded, the internal emptiness, and external emptiness, the emptiness of the large, and the emptiness of the small are alike as emptiness, and not otherwise." They are alike as emptiness, so how are they otherwise as "emptiness of the conditioned" and "emptiness of the unconditioned?"
As far as I'm concerned, there are no unconditioned "things." "Things," and by that I actually mean "dharmas," are not unconditioned. I personally don't believe in Theravāda's autonomous nirvāṇa-dharma anymore than Sarvāstivāda's two similar nirvāṇa-dharmas. I am somewhat committed to the stance of nirvāṇa not being truly a dharma at all, in that dharmas themselves are not dharmas, much less nirvāṇa. When the unconditioned is a dharma, when it is experienced, it gets caught up in perceiver, perceiving, and that which is perceived, and it gets "caught up" in the conditioned and is itself revealed to actually be conditioned. So in what sense do you bring up the emptiness of unconditioned things here (as opposed to conditioned things, I presume)?
I was once reading the Madhyamakālaṁkāra from Ven Śāntarakṣita, and imagine my surprise when I encountered the exact same objection as I raised to the Theravādin А̄bhidhammika conception of nibbāna:
(Madhyamakālaṁkāra on "Neither unity nor diversity," stanza 3, translation K. Lipman)3. Even according to the approach of those who speak of the unconditioned as an object of knowledge for a cognition which arises out of meditation, it is not a unitary (entity), because these (unconditioned entities) would be related to a cognition which has phases (of before and after).
It sums things up nicely IMO. I was glad to find it, because at least someone agrees. So with it in mind that you didn't mean "unconditioned things" in the sense that Theravāda and Sarvāstivāda mean them, what did you mean? Empty things in general? When things are empty, why say "conditioned" or "unconditoned?" My not understanding is probably an issue of language.