firewns wrote: “However, suppose that the being is either unaware of, or chooses not to obstruct tanha, so that it smoothly leads to upadana without much hindrance”.
Yes. That is why it is not possible to stop the rebirth process if one is not exposed to correct Buddha Dhamma.
On other questions:
“Tanha paccaya vinnana” does take place.
“tanha paccaya rupa” happens only indirectly. For example, one’s next birth (and the accompanying body) arises due to a built-up vinnana. This is a deeper aspect.
I suggest reading the following to understand what is really meant by vinnana. This is something most people do not understand. Vinnana is all about “future expectations”:
I recommend reading the posts 3 through 6 in the following section:
“Essential Buddhism”
and then read:
“Viññāna – What It Really Means”
It is worthwhile to spend the time and understand vinnana.