Doing a two-person party would add a lot of complexity to the mechanics, yes. Partner might not be out of the question though.
Viewing post in Chapter 2 Update: Some bad news, and some good news comments
exactly, my friend. Although it would be more fun, it would represent more work for you when programming the game. Also, you should make changes to the original idea and the script of the game. It's just a suggestion, and hopefully you'll manage to include a partner. but still continue with your original idea. that, if it's as good as the first chapter, it's going to be a success, again...