I have several pieces of source which are compiled for a generic 80C31 or a Dallas 80C310. These processors require a different include files for the sfrs. Rather than changing the source code each time I change projects, it would be nice to use an ifdef.
"The only useful improvement possible in this area..." Actually there is a really useful improvement that Keil could make here: They could make all the project settings available to the source code via Predefined Macros. Currently, only the Memory Model is available - via __MODEL__ So why not the others; eg, __XTAL__, __DEVICE__, __TARGET__, etc, etc.