Not really thinking of it for position.
I’m thinking of it more for things like slider max value, min value, etc. For example, when writing a plug-in, it is not uncommon to have a file full of constants defined for this as they often need to be used in a few different places (and for readability).
It seems like it should be relatively easy to change. I would guess the Jucer is storing a floating point value that is converted from the string entered into the Jucer. If that floating point was stored as a string and evaluated as needed (for example, when previewing the UI), this could be made to work. The Jucer could continue to work as it does for numeric strings, and set the control range to it’s current 0-10 default range when it gets a string, which, as you point out, it will not know how to parse.