My game idea.

I think most people have similar ideas when they first set out into the strange world of video game development. I know I did. After many failed attempts, I began to see some real issues with the idea. For example, RPGs are mainly selfless in the story and how the game progresses, while first-person shooters are more self-centered (selfish, even).
The closest I have ever seen to “first person game with puzzle elements” was the Half-Life series. Valve Software did a fine job with it in that respect, but the puzzles were usually quite lacking any real amount of logic. For a fine example of a puzzle which requires a high level of thinking, look no further than the ‘ice block key puzzle’ in The Legend of Zelda: The Minish Cap… Or any number of puzzles in The Legend of Zelda: Link’s Awakening.

Well, good luck to you, if you choose to go through with it.