This is a very simple mod that changes Trader Rekt’s stance from Dislike to Like. The result is that Rekt uses friendly dialog instead of being an @%$#, nothing else changes.
This mod works on existing saves, no need to start new.
You can change the stance from “Like” to “Neutral” if you’d rather not have him be friendly. Trader Hugh is neutral, for reference.
The forum topic of the mod is here.