My conclusions:
Vinnana in the suttas almost always refers to an established-vinnana. You can see this in SN22.53. When there is tanha, asava, anusaya, there is still an element that causes engagement, involvement. This means that ‘our’ knowing at those moments, out of force of habit, will direct too, and get involved with something; a feeling, an emotion, a thought etc. Our knowing establishes upon that.
In practice this is just the situation that our attention is caught by something and we are acutely aware of something. But it is also much more. “Caught” also means that our mind/knowing has become fixed and rigid. Our knowing is unwillingly directed towards something, it establishes out of force of habit upon something. It is also a moment of fettering.
So, this vinnana moment, this cognitive moment also represents an element of unfreedom, fettering. There is a certain rigidness establishing too.
Besides this, it is also a defiled kind of knowing moment. Because in this kind of cognitive moment there is always this element of engagement (tanha, anusaya asava). It is never without. So the understanding/knowing is also distorted at that moment.
So, vinnana is not merely being aware of something, a consciousness or bare awareness of something. Not at all. Rather when vinnana establishes on something this represents a cognitive moment that is 1. Defiled, impure, involved 2. Distorted, 3. Unfree or fettered, rigid.
When there is no element of engagement or becoming involved at all present (no tanha no asava, no anusaya), there is a situation that our knowing does not become established upon something, at least not unwillingly due to asava, tanha, anusaya. Not on a rupa, not on a Vedana, not on a sankhara, not on a sanna. The mind or our knowing remains open, empty, desireless, uninclined, undirected, vacant, free. This is purity.
It is NOT the nature of mind that we are trapped in a cognitieve process of being alternately captured by something seen, heard, felt etc. That is how a defiled mind functions but not a pure mind. We must not think that mind/knowing always alternately lands on this and then on that. Only defiled minds functions this way.
When the heart and mind are purified mind becomes steady. It is always vacant, and freed now. Open. Extremely pliant, easy to use.
When our knowing becomes established upon something. i.e. involved in something, for example an emotion, there is also a sense of Me knowing this emotion. It is a defiled and distorted cognitive moment. So, this is always also a self-awareness. Vinnana establishing always contains the dual notion of a subject/me/I perceiving this or that.
This is what the concept of vinnana expresses i believe. It is much more then consciousness. When ‘our’ knowing establishes upon something this also implies 1. Engagement/involvement, defilement, fettering, unfreedom, impurity. In short, a defiled distorted cognitieve moment has established, ie vinnana has established!
I have faith that there is also a knowing that is vacant, a knowing that does not become engaged. Pure. It does not establish upon something. It is desireless, empty, undirected, uninclined, signless. This is very subtle. It is open, vacant, empty, free, steady too.
One can also see this as a dimension of emptiness and clear light (knowing).
If you try to seek this vacant mind/knowing you cannot pinpoint it. You cannot find it nor describe it. It can never be sensed.
Besides having some intuitional understanding of all this, some feeling, great meditation masters from many Buddhist traditions teach that we can also have a direct meeting with this vacant and unestablished knowing. The citta, the buddha nature, the stable, the unconditioned, the deathless, the amazing, the wonderful, Nibbana dhatu. But it is not known by the senses.
Anyway, I am convinced that vinnana does imply much more then consciousness in the suttas. In practice and how the portrayed Buddha uses this concept, it refers to: an involved, engaged, defiled, impure, fettered, unfree, rigid, deluded, dual (subject-object) cognitive/knowing moment. In short: vinnana establishing.
In the core the Buddha, I feel, wants to open our eyes for this knowing element inside us that has no direction, does not establish upon something, remains uninvolved, is signless, desireless, transcendent, unwordly, the escape, island.