I have a component in MyPackage that uses a pointer to another component. Is this a bad idea?
This is an extremely bad idea.
If you use units from another package, add that package to your packages dependencies.
Remove any path config you added.
Well yes, it is possible to do something like this with pathes. But it needs a lot of knowledge, including knowledge off *ALL* other packages, and checking *ALL* of them whenever you do updates.
In short: It is almost guaranteed to go wrong.
If it goes wrong, you get duplicate ppu files. Some of them will get outdated. You will get random errors in your application. (because it runs code, that you don't even have anymore.)
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Once you removed the path config, go to your packages folder, and delete all .ppu and .o files.
(Or try forcing a "clean" build)