I’ve just taken a high quality scan of the reference image I’ve got of the Aesir Dreadnought from the Horus Hersey CCG. This captures the whole essence of what I’m after. Of note is the Thousand Son with holes in him under the Dread’s foot and the ‘shark tooth’ grin on the face guard for want of a better description. I may or may not choose to have mine thumping another Traitor Marine.
The basic concept is that the Space Marine chapters are still using a significant portion of the equipment that was created before the great betrayal. The capacity for manufacture is very low, so the chapters will treat every piece of equipment as slightly sacred/revered/etc. However in the ten thousand years of use equipment will have been repaired and replaced so many times that its original form will likely have been lost. Occasionally the tech adepts will discover the plans for a new piece of equipment, or a discovery will be made (put demolisher cannon onto rhino = vindicator) and slowly over a few centuries this will become more wide-spread.
As such the Dreadnought I’m building will be an upgraded version of the Dreadnought used during the Horus Heresy – although with a different entombed Marine and all elements of the Dreadnought having been replaced.