Can I cancel my consciousness?

If you mean cancelling consciousness as realization of emptiness, then yes, one can “cancel consciousness” as in everyone can realise emptiness.

Buddha might say, "change yourself keeping mindful of the dharma." But why is behavior modification necessary at all?

To end suffering, isn't it.

Why is rightness a requisite?

"Right" is an adjective which is applied to the path which the Buddha showed and which the wise found to be effective, i.e. which leads towards the end of suffering.

I understand it as an honorific title or like a proper name, i.e. which designates the (right or noble) eightfold path (and Noble disciples and so on).

Ariya as an adjective is juxtaposed 15 times in the four Nikāyas with niyyānika (leading out [to salvation], emancipatory). It can actually be understood as meaning 'leading to the end of dukkha', as explained at MN 12:

Yet, Sariputta, by such conduct, by such practice, by such performance of austerities, I did not attain any superhuman states, any distinction in knowledge and vision worthy of the noble ones. Why was that? Because I did not attain that noble wisdom which when attained is noble and emancipating and leads the one who practices in accordance with it to the complete destruction of suffering.

When used as a noun it refers to Noble disciples:

Ariya as a noun has been traditionally understood as designating an individual who is at least a sotāpanna. ... Some suttas imply that the word designates arahants.

According to SN 45.2 that arguably is a requisite. My personal experience is that I may learn from other people and that's such a basic and universal fact that I'm not sure how to answer, "why is it a requisite?"

In theory, the human is capable of performing its function, i.e., task completion, with or without consciousness, a natural robot for lack of better term.

I think an automaton may be "conscious" in some sense i.e. it's "with sense-organs" -- e.g. a robot might to be "self-aware" enough to know whether it's falling over and to take corrective action, yet still be just a machine, like some airplane with an auto-pilot (and pitot tubes and gyroscope and other "sense organs").

Later you mention "dual experience" -- it reminds me of a contemporary poem:

Self-Pity

I never saw a wild thing
sorry for itself.
A small bird will drop frozen dead from a bough
without ever having felt sorry for itself.

This poem may be untrue, and contrary to Buddhist doctrine, which has it that birds are "sentient beings".

But I think it's interesting.

Firstly I think it illustrates the "dual experience" or lack thereof that you're talking about, i.e. the "subject/object split".

If the human is destined to destroy the planet, why should knowing its status be mandatory?

Is this saying, "Woe! Why me?"

Because that's how I read it, i.e., "Take this cup away from me..."

Should I be penalized for not wanting to change my nature? I suggest consciousness be optional. For those that want to experience the world from the human position, they may elect so, but for those uninterested, the dual experience can be returned.

And this sounds like the "bargaining" that's one of the famous "stages of grief"!

Seriously though, one of the reasons I find the poem "interesting", even if it's wrong about whether the bird is suffering, is that for a second it takes me out of myself and has me imagine it (and therefore me) as a heroic or at least uncomplicated "robot", as you posited.

More particularly it evokes sympathy for the bird, even admiration.

And maybe that -- thinking of others -- is Buddhist, and an antidote to selfishness, and even a way towards the "natural roboticism" which you posit as an ideal, i.e. being aware of the world without yourself always being "the subject". That may be evident in the Mahayana viewpoint, I think it's evident in the Pali suttas too, e.g. in the story of Skinny Gotami & the Mustard Seed, where Gotami had "sorrow-to-the-point-of-madness" when "her" son died, and the fully awakened one cured her by exposing her to the larger picture.