I am not sure what you mean here.
Within alleged vestigial features that have specifically been claimed to be leftover remnants from a common ancestor, we should find function relative to survivability, reproduction, and fitting environments. This would show that there was a common design between those kinds of organisms rather than a common ancestor.
For instance, “The chirality of DNA, RNA, and amino acids is conserved across all known life. As there is no functional advantage to right- or left-handed molecular chirality, the simplest hypothesis is that the choice was made randomly by early organisms and passed on to all extant life through common descent. Further evidence for reconstructing ancestral lineages comes from junk DNA such as pseudogenes, “dead” genes that steadily accumulate mutations.” (Wikipedia)
Furthermore, “Phylogenetic relationships extend to a wide variety of nonfunctional sequence elements, including repeats, transposons, pseudogenes, and mutations in protein-coding sequences that do not change the amino-acid sequence. While a minority of these elements might later be found to harbor function, in aggregate they demonstrate that identity must be the product of common descent rather than common function.” (Wikipedia)
Read this for more:
Plagiarized Errors and Molecular Genetics (talkorigins.org)
This reasoning would apply to morphology as well. I have already gave an example of the Panda’s thumb.
I want to address another thing you said on the side…
Again, this study shows otherwise:
Biased gene transfer mimics patterns created through shared ancestry | PNAS
I might as well address something else you said that seems to be wrong…
I am guessing you disagree with Ernest Mayr on this point then:
“Given the fact of evolution, one would expect the fossils to document steady change from ancestral forms to the descendants. But this is not what the paleontologist finds. Instead her or she finds gaps in just about every phyletic series. New types often appear quite suddenly, and their immediate ancestors are absent in the earlier geological strata. The discovery of unbroken series of species changing gradually into descending species is very rare. Indeed the fossil record is one of discontinuities, seemingly documenting jumps (saltations) from one type of organisms to a different type.”
From “What Evolution Is” Ch.2