I think this is where we part company on our lexical understanding of hetu-paccaya. I follow the consensus that in the EBTs, the 2 are synonyms; it is only in the Abhidhamma that a distinction is drawn between them.
You can see this equivalence in the waxing syllable phenomenon of “ko hetu, ko paccayo” pericope all over the suttas. My favourite example is SN 22.82 -
Ko nu kho, bhante, hetu ko paccayo rūpakkhandhassa paññāpanāya; ko hetu ko paccayo vedanākkhandhassa paññāpanāya; ko hetu ko paccayo saññākkhandhassa paññāpanāya; ko hetu ko paccayo saṅkhārakkhandhassa paññāpanāya; ko hetu ko paccayo viññāṇakkhandhassa paññāpanāyā”ti? “Cattāro kho, bhikkhu, mahābhūtā hetu, cattāro mahābhūtā paccayo rūpakkhandhassa paññāpanāya. Phasso hetu phasso paccayo vedanākkhandhassa paññāpanāya. Phasso hetu phasso paccayo saññākkhandhassa paññāpanāya. Phasso hetu, phasso paccayo saṅkhārakkhandhassa paññāpanāya. Nāmarūpaṃ hetu, nāmarūpaṃ paccayo viññāṇakkhandhassa paññāpanāyā”ti.
What is the cause and condition, venerable sir, for the manifestation of the form aggregate? What is the cause and condition for the manifestation of the feeling aggregate?… for the manifestation of the perception aggregate?… for the manifestation of the volitional formations aggregate?… for the manifestation of the consciousness aggregate?”
“The four great elements, bhikkhu, are the cause and condition for the manifestation of the form aggregate. Contact is the cause and condition for the manifestation of the feeling aggregate. Contact is the cause and condition for the manifestation of the perception aggregate.
Contact is the cause and condition for the manifestation of the volitional formations aggregate. Name-and-form is the cause and condition for the manifestation of the consciousness aggregate.”
Other suttas supporting their equivalence would be -
DN 34, AN 8.2 - paṭhamo hetu paṭhamo paccayo ādibrahmacariyikāya …
SN 42.9 - aṭṭha hetū, aṭṭha paccayā kulānaṃ upaghātāya…
AN 8.70 ditto for cause and condition for earthquakes
Do you actually have any textual support from the EBTs to back-up your belief that hetu and paccaya are not synonyms in the context of discussions on conditionality/Dependant Arising?
As for this -
I think too much has been built into this interpretation of Dependant Arising. I’ve actually surveyed the Pali suttas for how the short catechismal listings of DO (eg the list in SN 12.1) are applied and explained, and the sense I get is that DA is always applied in retrospect after the First Noble Truth is established/accepted. I’ve not actually seen a sutta that applies DO/Second Noble Truth to predict a particular aspect of Suffering will come to be. DA is always used to explain how bhūtamidaṃ (this has come to be) (SN 12.31 and MN 38) came to be.
Nowhere is this clearer than in DN 15, where Dependant Arising is explained as follows -
‘Bhavapaccayā jātī’ti iti kho panetaṃ vuttaṃ, tadānanda, imināpetaṃ pariyāyena veditabbaṃ, yathā bhavapaccayā jāti. Bhavo ca hi, ānanda, nābhavissa sabbena sabbaṃ sabbathā sabbaṃ kassaci kimhici, seyyathidaṃ—kāmabhavo vā rūpabhavo vā arūpabhavo vā, sabbaso bhave asati bhavanirodhā api nu kho jāti paññāyethā”ti? “No hetaṃ, bhante”. “Tasmātihānanda, eseva hetu etaṃ nidānaṃ esa samudayo esa paccayo jātiyā, yadidaṃ bhavo.
“It was said: ‘With existence as condition there is birth.’ How that is so, Ānanda, should be understood in this way: If there were absolutely and utterly no existence of any kind anywhere—that is, no sense-sphere existence, fine-material existence, or immaterial existence—then, in the complete absence of existence, with the cessation of existence, would birth be discerned?”
“Certainly not, venerable sir.”
“Therefore, Ānanda, this is the cause, source, origin, and condition for birth, namely, existence.
See also how DA 13 expresses the same notion of dependency/conditionality in the parallel passages.
Can you see how Dependant Arising is explained vide the negative existential locative absolute (bolded) used in Cessation? This is quite clear that DA purports to explain the necessary condition for a consequence, not that the condition is sufficient to give rise/cause the consequent.
That being the case, does your hypothetical concerning consciousness being a hetu/cause for Suffering apply Dependant Arising properly? You are using Dependant Arising in a predictive manner, but as the longer exegetical suttas demonstrate, Dependant Arising is used to explain how Suffering has come to be, not that Suffering will come to be.
Surely you must be familiar with the notion that the Attainment of Cessation takes place despite the presence of the Six Bases? If Dependant Arising were inexorable and predictive as you put it, it cannot account for Cessation taking place despite of the Six Bases.