Load EXE as DLL: Mission Possible
You have been warned not to load an executable with LoadLibrary(), you have probably tried to do so and your application crashed. Therefore you thought that it is not possible.
This is somewhat against what Microsoft has to say about it. Actually, they never say "don't load it". They just say "don't use LoadLibrary() to run an executable, use CreateProcess() instead". Who said anything about running the EXE? Therefore, what I will present here is compatible enough, at least for the mighty reader. But don't use this stuff in production code unless you know very well what you are doing. You have been warned.
The first required thing to do is to mark the executable as relocatable with the ability to load at any base address (as any DLL). This is done with the /FIXED:NO, and you can improve security by using /DYNAMICBASE (which is on by default) as well. EXE files might be linked with /FIXED:YES in which all relocation information from the executable is stripped and the EXE can only be load in it's prefered base address, which, unless set by the /BASE option is 0x400000.
Do not load the executable with LoadLibraryEx() specifying LOAD_LIBRARY_AS_DATAFILE or LOAD_LIBRARY_AS_IMAGE_RESOURCE. Doing so will not export the exported functions from the EXE and GetProcAddress() to it will fail.
