The examples given are definitely challenging to consider.
I would be in favor of documenting some “simpler” interesting and desirable examples in spec itself with sample browser renderings.
For example an inline flow element that is wrapped across multiple lines, both where the boxes are disjoint, and where the boxes are touching, or perhaps wrapped across 3+ lines, to illustrate an “outline that encloses all the element’s boxes” as a more ideal rendering than say separate boxes for each piece.
Perhaps related, the spec mentions non-rectangular (effectively) three times in the outline section, “Outlines may be non-rectangular” (twice) and “The parts of the outline are not required to be rectangular”. While clarifying/documenting some preferred outline renderings, perhaps we can simplify the definition and remove the apparent duplicate descriptions.