Yes, it makes sense. No, you can't do it with Creo. There is no ability from relations to control whether a dimension is 'reference' or 'strong'. It might be possible from Toolkit, but that is expensive and most don't have it.
What I do in these situations is create the second dimension so it's controlling something else entirely, typically a point placed on an axis or construction line. Using your example, if dimension_type = F_F, the "24" dimension will be used and the "24-27/32" will not. If dimension_type = P_P then you use relations to take whatever value is entered for the "24-27/32" dimension and use that to set the 'real' "24" dimension. (This is easy to calculate since it's just a triangle.)
To make it more user friendly, you can create an extra layer with layer rules to automatically add the unused dimension to it based on the current parameter value. The end result will look and act like what you want, it just takes a little more effort to create the illusion.