First, Nothing below is a definitive answer, either positive or negative.As you know, we don't have clear guidelines/policies for that question.
I'm trying to get a better understanding first, and I'm open to changing
my mind. :)
There are two different questions in your email, even if it's not
explicitely stated: naming that image "Debian image", and naming that
image "official Debian image".
Given the amount of customization you describe, my current feeling is
that naming that image "Debian image" should be approved, and even more
after you switch to using a Debian-provided kernel.
Now, "official Debian image". I don't think that for EC2, "official" has
been explicitely defined. It could mean "generated and provided by
Debian", "recognized by Debian as being 'pure'", but also "part of the
list of default images on GCE" (that would be "official" from the GCE
POV, not from the Debian POV).
Could you clarify what you are aiming for?