Certainly I can make these private methods, nothing else should be using them.  It's a little tougher to unit test, but of course they can be.

As for a reference to another asset, that's not the way I understood the pathresolver.  It seems that both the pathResolver and the new AliasPathResolver don't really point to assets directly.  It's more a glob or pointers to a directory and matches anything in the directory.   Since this is all set in config, it seems like it should make sure that set path exists.  If it doesn't, one has no way of knowing that the reason their asset doesn't resolve is a configuration issue since the resolve method simply returns false if it can't find the full asset.  Am I over thinking this one here?