carolina reapers, trinidad scorpions, and ghost peppers. novelty and spiciest peppers in the world. ppl grow these indoors all the time for the control factor. you can have this predictable environment to hone in on making them even spicier. increase heat when fruiting, bring them close af to the light, etc.
or say you're going to be breeding plants and selling them on ebay. ask the hydo dealer if he has any recommendations of pricey plants. it'll give you insight as to what this guy knows and what kind of plants he's concerned himself with.