On the other hand here stands the discription that nibbana is the highest sukha, it is pleasant (and so here we have that "endless mind" theory of Ven. Thanissaro and some other teachers, and critisism of "no self" as wrong opinion, since Buddha didn't say that there is no self =).
I believe I've seen it stated in the suttas more than once that Nibbbana is the highest happiness for the very reason that it is separate from the aggregates, but not because there is something there which is perceiving "happiness", the lack of any conditioned phenomena is the very thing that makes it peaceful. I cannot cite a source on that, I'm just going by memory, maybe someone knows what I'm talking about? I've heard some teachers rationalize that nibbana must involve some degree of perception, but not Thanissaro or any other Theravadin. I like Thanissaro, though I'm not a follower of Thanissarodhamma over Buddhadhamma, and I can't help but feel like you're misrepresenting him a little on some of these issues.
On "consciousness without feature", maybe I haven't read closely enough, but I haven't read anything that suggests that this is something attained upon the death of the Arahant, but rather is related to the experience of the Arahant while still living. I feel there's a similarity between this, and the simile of "consciousness without landing", meaning non-manifestive consciousness, the consciousness of the Arahant that does not delight in, grasp at and proliferate for the sake of any sense-object, as described by http://www.accesstoinsight.org/tipitaka ... .than.html.
"If a monk abandons passion for the property of (whatever object), then owing to the abandonment of passion, the support is cut off, and there is no landing of consciousness. Consciousness, thus not having landed, not increasing, not concocting, is released. Owing to its release, it is steady. Owing to its steadiness, it is contented. Owing to its contentment, it is not agitated.
But then of course even this consciousness will cease upon the death of the Arahant, I don't see any reason to think otherwise.