Concoctive is a relatively uncommon word with only a few synonym options available. One possible replacement is creative, which highlights the imaginative and inventive aspects of concoctive action. Another synonym is innovative, which emphasizes the novelty and originality of the ideas or solutions being concocted. Resourceful is another option, as it captures the sense of using available materials and skills to create something new or solve a problem. More broadly, brainstorming, ideation, or problem-solving could also be used interchangeably with concoctive if the focus is primarily on generating ideas or solutions through a process of creative thinking.