I would love to hear about e challenges of making a hybrid rpg / adventure game. How you strike the balance of getting the right amount of rpg elements without disturbing the adventure feel. Also about what affect the rpg elements have on development and testing times.
Hey mate, good to hear from you! I'll add to what Steve said, because I have done a lot of the work with the stats.
The main difference between this and a standard adventure game is that the stats effect the ability to do something. So for example, in one of the Kings Quest games you jump and grab the eagle. If that was in an stat driven game you might need a "jump" stat of 50 to grab the eagle or you'll fail. So it just adds another level to the game. From a design point of view, it's not too much more difficult to design in this way.
The difficulty, as BT said, is where to draw the line. We want to have an adventure game with RPG elements, not an RPG. We design the game as an adventure, we wrote the story first, then we overlay the stat side of things onto the story.
Another thing is not having too many stats to play with. We've got 10 stats in QFI, 5 of which are directly related to combat. The other five are specific activities. Athletics covers everything like jumping, climbing, throwing etc. Bluff, Stealth and Thievery are all for sneaky activities. Influence is how much influence you exert over other people. All these things are very much about driving the story forward, which is what we always want to do.
The other thing we've got in our game is hard caps on the stats. While most stats will go to 100, if you're not a rogue sub-class you won't be able to get Thievery above a certain level.
Honestly, most of it is just a gut feeling. We do what "we" would like to play!