I have a couple of saved games from different modules. All of the saves have the same character, but are at different levels. Is it possible to replace older characters with the most recent version? I wasn’t sure if just replacing the player.bic file withing the save folder would do it or not and I don’t want to go screwing up my saves.
Load the saved game with the character you want and save the character. Next, start a multiplayer game, loading the saved game where you want to import the character. Choose the saved character you want to import, and then use that character, not the one in the saved game. Once the game is loaded, save the game again (in another file, to be safe). Exit and go back to single-player, loading the new saved game. Enjoy.
If your character that is being replaced has any quest items, you’ll lose those. You might be able to drop the quest items on the ground and save the game before importing the other character, but some quest items cannot be dropped.
Thank you very much for this trick, @Empyre65 ! 
It helped to save one of my save games! 