What exactly are you doing? I've messed with my 4 player mod a little bit trying to get Jahan to have 1 stats with stat poitns. I've managed to get him to all 1 stat points(and can change whatever else in characters.txt with no issue). All I've done is include the characters.txt into my mods folder. Here's where mine is.
Example: G:\Program Files (x86)\Steam\SteamApps\common\Divinity - Original Sin\Data\Public\4Player_-_Test_1ddd6993-6d9b-4e71-a437-1195dd217cf6\Stats\Generated\Data\Character.txt
Did you copy the whole Characters.txt from the main mod, or did you create an empty one with just Jahan?
If we need all stat entries to be in Characters.txt to work then it'll conflict with other mods (and the main mod) so it'd be pretty useless
The whole thing, or at least that is what I did, I didn't try it with just him. I'd assume you would need the whole file though. This would certainly conflict with other mods using this file, but not the main mod. I mean it overwrites it, so how is that conflicting with it, if it uses it's data but modified?