It's discutable if this should work. But the quickest solution for this would be to allow for a small change in the "Write Key (Variant).vi" and "Read Key (Variant).vi" in the Cluster case similar to this:
I had these 2 links concerning re-factoring in my archive
http://labviewguy.com/refactoring/
http://www.ieee.li/pdf/viewgraphs/refactoring_labview_code.pdf
They help break it down into parts to think through but I've not found any silver bullet when it comes to re-factoring.
I always seem to have lots of backups and forced to do lots of testing. Commiting often to Source code control was a big help in my last re-factoring project.
Mark
Use the default value property (assuming you have a control reference) as input to the Application Method aptly named "Data Type Color".
This is where the class browser Ctrl-Shift-B comes in very handy.
Also works in conjunction with wires and control terminals.