That's a very good suggestion, Carl!
The main challenge I see is that for the current version of "copy as guide to all precomps", you need to select the layers which you want to copy. Hence, the tool needs to be able to distinguish somehow, which layers are the ones that you want to copy and which are the precomps to which you wanto to copy them.
Solution 1)
We could split the selected layers into the ones that are precomps and the ones that are no precomps. Then we copy only the latter. However, this would make it impossible for you to copy a precomp to all other precomps. Also then it is rather unclear how to deal with precomps inside other precomps (should we not copy to them at all, or to all of them or again only to the ones that are selected?).
Solution 2)
Instead of limiting the precomps to only selected ones, we could limit to only precomps that are not lockled. That would mean before running the tool, you simply lock the precomp layers which you don't want to process.
In this video I show how to implement solution 2:

The extended version of the tool with the locked precomps option will be included in the next beta update 🙂