The problem is to make it occur in an existing save game (to continue on from storyline) you need to edit the save game.
2 ways to achieve what you want.
Use the save game editor and set all the factions to 0.0 or something for you.
Edit the last mission, adding some code so that at the end of the mission ALL the reputations are set to 0.0 (see open SP for the example of code, youāll have to find where to insert it) - then load your last save game before the mission was completed and re-do said mission. As part of the successful completion of the storyline you will get everyone loving you.
However, whilst you may like to just explore, the game will become HELLA boring if everyone is friendly š Much more fun if you have to hack reputations every now and then, or try and become friends with folks etcā¦
Either of the above are possible, which would you prefer? Iām sure more help can be given as to what you need to do š