Alright lets see if I'm getting this.
In your pretty voice example, Just adding the trait will give the non stat affect of increasing merchant performance? You'd have to add the stats your self and the "effect" is redundant, unless you were planning to later remove the trait.
So do all the traits work, apart from their effect stats for the purpose of being called on for jobs, or do I have to add the mostly redundant effect as well so it can be checked?
The MC's got a MC field for their spec that does nothing if given to a slave and they've got a slave spec which uses there mc spec but since its in the slave spot it does nothing and I was wrong to assume one was so it appear in the character sheet and the other was for its stats. You can use slave spec in the second spot but they're of course not usable in jobs, so only good for combat and exploration. Ones like assassin, body guard, ranger, and trapper would work I assume, but the rest nah.
The tattoos are irrelevant in terms of stats if you're only using save editing. You might for instance choose one for its effect and change them in the save for "aesthetic", or add them in game and remove them in save to add some more to receive multiple effects, but that's just excessive. (Not at all tested just speculating)