>>96294698
Run a game. Have a clear, concise concept in mind. Maybe do something that GURPS handles better than other systems, like some kind of cross-TL/genre mashup. Let the players get creative, and tell them how they can actually do that thing within the rules rather than it either being expressly impossible ("Erm, that's not a class ability or a feat so...") or handwaved ("Well there aren't any rules for inventing new devices so uhhh just roll a d20 for how good you do".) Let the system sell itself. If you run it, they will play it - at least once.