Why aren't there symlinks for things standard linux directories, a bit like current-system in the user environment? Why go through the effort of patching the ac

Why aren't there symlinks for things standard linux directories, a bit like current-system in the user environment? Why go through the effort of patching the actual binary? Doesn't that cause enormous problems with signed stuff? Edit: I assume you can't do it very well system-wide because individual packages might need conflicting versions. Okay. Has something like runtime injection been considered? What are the trade-offs here? (I think it's fairly obvious that I'm not very familiar with the whole matter yet).