as a player,i don't agree with that, but as a modder i see your point a bit, i like half of your idea, a nice feature like "opposites trait" when you can't chose same trait as example if you chose "Dekamelon" you can't chose "PettanMikan".
I'm mean it sounds like you're completely onboard with the idea, whether it be mutual exclusivity for traits or a hard number of picking 3 out of 8 traits. I just want there to be the option if author has a specific vision for a 'vanilla' playthrough of their world. Meanwhile the player can enter the editor and disable the trait limits if they want to do so.
I don't see what's wrong with asking for that. I'm not asking to password protect or lock the editor, so that the players are stuck with the trait limits. It's more of a person waving a sign saying, "Please only pick two." Or "Please don't pick Futanari and Femboy at the same time."