Microchip XC8: How to Overlap Specific Variables without Union?
I find unions perfectly fine for "sharing" variables. Let me expand on this with code:

typedef struct
{
  union
  {
     struct
     {
     } set_1;
     struct
     {
     } set_2;
  } set_union;
  struct
  {
  } set_3;
} data_set;


... Of course, this could be made much more readable using typedefs on set_1 and set_2.