Joined: June 2004
The issue is not that you did not correct the issue in your example - it is that you repeated the error in your main argument. If you are prepared to make the appropriate modification - rather than labelling it an "assumption" then that problem is solved.
Now similarities in human designs are to an extent a reflection of human limitations - reinventing the wheel is a mistake in human terms - but obviously a being that lacked those limits would not necessarily produce that degree of similarity.
Indeed it seems that rather than relying on a sample, you are trying to reason from the properties inherent in being an "intelligent designer". This might be a better approach in the absence of examples of non-humans to sample but it is a different approach and renders your initial post irrelevant.
Not being any sort of art critic I will not attempt to offer any detailed description of stylistic and aesthetic considerations. But it is clear that an artist will tend to use particular motifs and produce results which please his eye. Because these considerations are not functional AND can be expected to widely cross the (presumed) lines of descent they represent the best sort of similarities to use if arguing for an intelligent designer of life.
Structural similarities are far less useful to you for reasons discussed in the earlier thread. You might have some hope of arguing in the grounds of lateral transfer of "designs" but so far as I am aware that approach is not supported by the evidence.