Yeah, I tend to have those good ideas now and again.
The action tree interface would certainly make the game easier than the text parser, because when you're talking to an NPC or click on an object you can see all game-relevant questions and actions. Some people might not think that would be as fun or challenging, but perhaps to get the most out of NPC's - and thusly get full game points - you'd be challenged to pick the correct questions and responses from your character (Some would be very similar, thusly only through trial and error would you be able to figure out exactly which is correct)) from a conversation tree.
Ah, but then if you keep the text parser, you can add easter eggs into the game, that if when certain phrases - some obvious, some not so obvious - are typed in, you get funny little responses or game animations. Heh. And perhaps the text parser could even be used to include game hints, spoilers, and cheats/solutions when certain extremely random phrases are typed in!
Now I want to write/make an adventure game, just so I can see if I can put these ideas into practice.