I hesitate to enter this discussion, since I do not foresee this ending profitably, however I'll try.
The crux of where your perspective on this particular matter of nibbana vs annihilation seems to lie in your definition of existence, which you define as "presence of mind and/or body."
Can I ask a question in relation to that. Does this sentence mean to you...
1. The ontological independent existence of a biologically living organism
2. The phenomenological experience of mind and/or body
If you take it to mean #1, then it is no wonder you take permanent death itself to be goal.
#2 on the other hand, describes a qualitative experience. If experience is conditioned by ignorance, then the consequences of #1 & #2 are pretty much the same. However, by transcending ignorance and seeing through all false perceptions of self within the five aggregates, the Buddha developed a unique mode of perception
not conditioned by ignorance, which involved the absence of sankhara.
Again, we're likely to come up again interpretive road-blocks here as you're likely to regard sankhara in this context as past kamma, rather than in its more common sense of something which is dependent upon something else (in this case, explicitly stated as ignorance).
Now, the mode of perception
or mode of existence
discovered by the Buddha is unique and is what constitutes the essence of the Dhamma. It's not merely a way to avoid the "ontological independent existence of a biologically living organism", but it's a means by which to experience nibbana here-and-now (i.e. not waiting until death). It's an enlightened mode of perception that lays down the burden of the five aggregates and the six sense bases, and doesn't engage them in a subject-object relationship. It is not 'existence', or 'being' or 'becoming' by any referrent with which we are familiar with as puttujanas.
I could say more, but I'd inadvertently find myself doing a disservice to those who explain these subtle matters of the Dhamma far better than me... on this subject, the works of Nanananda Bhikkhu are paramount and you'll find much of interest in the Nibbana Sermons to really stimulate thought on the distinctions raised in this topic.
Now, I don't know your motivation for participating in this topic. It may be simply to express your perspective, which is fair enough and I don't want to degrade the potential value of this. However, if you're not fixed in your views (and let's be honest, who short of a stream-entrant should be?) and prepared to explore well considered, well reasoned, well explained alternatives to existing frameworks, the Nibbana Sermons are seriously worthy of investigation.Nibbana Sermonshttp://www.what-buddha-taught.net/Books ... rmon_8.htm