Nested Parent-Child Packages

I have a fairly simple SSIS project that has nested parent-child packages.
I am trying to find the best way to manage the connections strings so as to make the package portable across machines and environments. Currently there is one "master" package which calls 6 child packages. 1 of these child package calls 3 child packages of its own.

For the database connections, I've settled on creating a standardized .dtsConfig file for each server/login. This is a relatively small number (intially 8) that I don't expect to grow much.

I've taken a different approach for the file-system connections used by Execute Package components that call the child packages. For each package that has child packages, I store all the connection strings (paths) to the child packages in a single .dtsConfig file. This works well for the top-level "master" package where I can pass in the .dtsConfig file (that has the paths to the child packages) as a run-time option in the Execute Package Utility.

However, this approach seems to fall apart for the 2nd generation package that in turn call 3rd generation packages because I don't know how to get the .dtsConfig file (with the 3rd generation .dtsx package paths) path to this downstream dtsx package.

Though I'm sure there are others, the only two solutionsI can think of now are
(a)don't nest packages beyond 1 parent/child relationship -- not really an option or
(b)Store the path of .dtsConfig files for each .dtsx package as an environment variable on each machine. This option is unappealing because it would require adding an environment variable for every .dtsx package that has child packages. I don't think it would take long for this to grow into a large number, that would make managing environment variables cumbersome.

So far my experience with SSIS has been that there was a simple solution for each scenario I had. So this hoop jumping I'm going through seems to indicate I am just missing something.

Is there a better way I am just not getting?

In a similar situation, I put all the 3rd level child packages in the same folder. Then I used a parent package configuration to pass a root path variable from the 1st level master to the second level master. I used an expression on the connectionstring property for each file system connection that concatenated the root path with the name of the package.

It worked pretty well for me, but there are some limits with parent package configurations, since they are evaluated later in the process than other types of configurations (hopefully something that will be addressed in Katmai).