Why no Find/Replace a variable with a variable?

Seems like a crazy omission! Why is there not the ability to do a Find/Replace a variable with a variable? There is the ability to run Finds for a particular variable name (although you have to type in the variable name - why not have a drop-down list of all the currently defined variables so you can select the variable you want to search for?), but there is no option to replace a found variable with another (different) variable.

In my particular case, a predecessor created variables that included product version numbers in the variable name. When a new version of the product came out, a new variable, with the new product version in the name, was created and applied to each occurrence of the variable for the previous version. That, of course, completely negates the purpose of variables! I'm trying to genericize these variables so there is one Product Version variable to deal with. However, having created the generic variable(s), there is no way in FrameMaker to Find the old variables and Replace them with my generic variables.

This seems like a major oversight in the FrameMaker Feature Set. Please address!