Use Multi-Player Save in Single-Player and vice versa

I am looking for a way to use my Civilization V multiplayer save in single player. Background is that I play a lot of games with friends but they quit once it is clear who is winning. However, I would like to play it to an end. Some for achievements, some for fun. It seems that you cannot do this.

On the other side, I would love to play some round where I have a hard time with a bot with a friend or two. Is this possible? Can you just edit a value in the save game that states what type it is? If so which value?

I cannot even see the save game from multiplayer if I start single player. If I copy it manually in the right folder it appears but the start button is disabled.

I can play the game if i start multiplayer and make my friend a ki. But I have the feeling that multiplayer and single player ki are not the same.

UPDATE: I own G&K and also BNW. Looking for a solution for the newest version.

The closest to using a multi-player save in single-player is to kick the Humans. When you load the multi-player save, you will be in the multiplayer 'Staging Room'. By selecting the red X next to a player you will 'kick' them, so that they are set to AI. Although it will still be launched as a multiplayer game, you will be able to play without the other human players. See images below.