I will admit I still have a slight interest in working on FDS games, but the system is so much more of a pain to work on than the NES. When I finish most of my backlog, I'll probably pick up an FDS game. I've thought about doing the Famicom Detective Club games, but something like Mr. Gold or Time Twist interests me much more. In fact, Time Twist uses some kind of compression for its text that I'd have to reverse engineer. It's a challenge I'd love to tackle.
Time Twist seems to have an interesting plot/setting(s), it's probably more fun to play than Mr. Gold all things considered (the latter is apparently very short though). Dead Zone is another game that could be potentially fairly interesting I believe, or at least historically important. As far as Famicom adventure games go, Ripple Island must have been quite advanced for the time, with multiple endings and all. Not a bad effort by Tokai Engineering.