I still cannot understand the context of your situation but the thing is if you want to add a column at runtime dataflow will crash like it has never crashed before, as SSIS has strongly-typed metadata which means you cannot change it at runtime.

So either you will need to create the newly package on or update the package at the design time.

if you want to change it on run time then you will need to do this

Developing a Custom Data Flow Component

OR

you can also see this Stairway to Biml [/url]

hope it helps