If I were designing a bunch of living things, I would do a lot of reuse. I'd pretty much design each separate animal by modifying the design of other animals like it.
But would you only sample from one ancestor? Why, when we were adapted from climbing trees to running on the savanna, did our designer elect to twist chimpanzee feet into some weird new shape instead of just borrowing the feet from ostriches or something?
I'm a programmer and an engineer I don't buy this re-use argument. When I make a new design, I sample from everything I possibly can, not a single predecessor. Also, if I were designing a whole multitude of things, there would be a lot more orthogonal modularity and a lot less tree structure. And probably some level of purpose in the designs.
The tree structure is very much strong evidence for unintelligent evolution.
I think you are right, but overstating it. That is, the tree structure is an argument for "local only" communication, as you say, why don't bird feet show up in any mammals and so on. Why are the changes across the tree incremental (which incrementalism is how we can connect adjacent nodes in the tree structure).
We do see a little bit of this in car designs. For modern cars one would have the major phyla which might be the brands, or possibly even the manufacturers. Within a given manufactured platform, there would be many similar offering...
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