On 12/5/2017 at 3:36 PM, thesargento said:

So my question is: Where to start to turn an MMORPG into a single player game?

 

If you have the code. You use break points to find the pesky bits you dont like and bypass it. Next you code out the dependencies on the code you bypassed. Rinse repeat. 

If you dont have the code then your hacking a game and you will need to learn asm and c++

Either of these will be years worth of labor and learning. Both can be done but I would expect you could program a clone yourself quicker. By example their were folks hacking a D2 trainer for over 2 years and it wasn't complete at the end of the day.

Good Luck!