Types of each argument to clr APIs must be known to compile - OverloadStrings can brake compilation
The clr API functions currently need to know the a lot about the types of each argument provided so that it can figure out the overload resolution.
This becomes a problem when supplied as arguments, numbers without signatures.
Additionally OverloadStrings means that each literal string needs the corresponding String or Text signature to compile.
Since all overloaded strings map to the same System.String, there's probably a few tricks that can be done to make this a whole lot more flexible.