Hacking address range mapping

[FunThomas]

it would be nice if someone could bring some light into the dark

i read very often about the address range mapping is different and changes between the kernels ...

could someone please try to explain or give me some links to read what different versions are out there, why they are different and what advantages exists of each mapping ?

and why is it so complex to make one mapping that works for all

i think it should be these lines in src code:
#ifdef LOADIINE_MEM_MAP //start of region
kern_write((void*)(KERN_ADDRESS_TBL + (0x12 * 4)), 0x10000000);
#else //only around coreinit region
kern_write((void*)(KERN_ADDRESS_TBL + (0x12 * 4)), 0x31000000);
#endif
#endif
//give that memory area read/write permissions
kern_write((void*)(KERN_ADDRESS_TBL + (0x13 * 4)), 0x28305800);

would be nice if someone could explain for a noob of wiiu memory management

thx in advance