Compare the Avro Tudor never-builts, that were modifications and developments of actually built airframes - they were easily able to be drawn with an accurate detailed paneling displayed.
Conversely, these HP airframes look bare without panel lines, but when there is no built aircraft - even one vaguely related - to act as an "educated guess" model, sketching in panel lines as a measure to just pad-out the picture doesn't add to the historical accuracy or "validity" of the diagrams - if anything it detracts from it. For the H.P.108 here, published drawings show the planned internal ducting structure of the wings for the internal airflow, so I included that detail, but there is nothing I have found to detail the fuselage structure - especially as there are multiple models designed with the same fuselage cross-section but completely different window arrangements which then doesn't even hint at a common internal rib-and-stringer structure. There are a couple of designs coming up that don't even have the flight controls drawn into the wings and tail, and as that detail wasn't included in HP's general arrangement sketches there is no idea how they would be sized (some similar designs had them big, some small).
Painted up in potential customer colours would also make the illustrations more rewarding, but going back to the "validity" argument, for these type of "historical record" series of illustrations, I've chosen to only colour up actual aircraft as constructed or displayed as manufacturer's promotional models - with only a couple of exceptions that I think speak for themselves as to their "historical potential". I coloured up the potential atomic bomber Lancasters as Enola Gay and Bock's Car as they may have been if the US had taken up manufacture, and then the almost bought South African Victors (I chose not to model the less likely Australian Victors). In a slightly different context the Saro Duchess painted in the colours of the planned initial customer TEAL, and the Saro Princess developments painted as the VC10's that instead took their place. So maybe not real, but as almost real as possible.
So, I'd love to flesh out some of these models, but for the designs that didn't progress much beyond "back of a napkin" sketches, I don't feel that it works in this context.