Execute package task external reference mode SQL Server

Hi All,

I was trying to use the SQL Server  as the external reference for the Execute package task for my parent package but it was showing me the msdb database content when I created the connection to the SQL server instance with catalog as SSISDB so that i could use the deployed packages as my child packages.

Actually  my denali msdb doesnt have any packages deployed to it.

My questions are:

1. What is the purpose of msdb database in denali if the packages are going to be stored in SSISDB?
2. What is the purpose of the SQL Server as external reference if we cannot deploy the packages to MSDB database as package configurations seems to be deprecated in denali due to project deployment feature and parameter feature?
3. If I want to follow the best practices and use the packages deployed in SSISDB database as my child packages what should be my approach other than using a stored procedure? 

Can anybody help me on this?

Thanks, Franco.