Jumping in, you're right - it is a weird way to organize a project, running
totally counter to the Work Breakdown Structure that is at the core of the
Critical Path methodolgy that is the basis of Project's design and I'm
certain that sooner or later the implications of this non-standard WBS are
going to rear up to bite you and get you into a major bind. Be that as it
may, what you're asking is certainly do'able but you'll have to implement it
in VBA. You can't use the Resource Initial column from the resource table
directly while renaming it the Linked Column because if you do, having your
procedure write "P" into the linked column for all tasks with Feature ID 001
in your example will assign "Peter" in the Resource Name column for all
those tasks. Instead, use one of the Text fields 1 thru 30 and rename it.
Then you'll need to write a VBA procedure that is triggered by a change in
the resource name column for any of the tasks that a:retrieves and saves the
resource initial from the resource table for the name you entered, b:saves
the task feature ID for the task you've modified, c:locates the first
instance of that task feature ID in the table, d:steps through all rows
matching that id and writes the saved initial into the linked column field
for each task in turn.