No need to get snippy

What wrong I said? Just question for ideas...

Means, that you will most likely not find a prepared, ready to use solution.

I understand it.

overlapping AABBs allowed ? Min/max size of AABB ? Are AABB allowed to include vertices ? Min/max number of AABBs per Mesh ?

overlapping - yes; size - as max as possible; including vertices is allowed, but not too much(5-10% by all); number of aabbs - from 1 to 4-5

navigation mesh

yep, it's really good idea.
get 3 planes, at x, y, z axis aligned and it will be contour of x, y, z projection of mesh.

hard problem here is:
How to simplify projected countour(3d mesh projection to 2d plane by orthogonal camera, using software rasterizer) to minimum vertices?