^Exactly, making a good Thief game should not be a difficult thing, i mean all you need is:
1. Graphics engine that isn't shit and can handle shadows
2. Good level design
3. Non retarded AI
4. Decent stealth mechanics
5. Stephen Russell
6. A non retarded story
7. Atmospheric sound effects and art style
8. Main hero who is weak in straight up combat
Oh, and moddability.
When it comes to technical issues the answer to all of the above is "it's 2014 and i want to hear no excuses." The main obstacle to a good Thief game is the designer's will to choose to implement those things and not cave in to consolitis(budget wasted on cinematics, small levels, everything spelled out for you etc.)
to all the above, save for
8. Straight up combat in Thief should be a loosing affair, I completely agree. But that should be because being in combat results in Garret being swarmed by guards, crossbowmen, etc. And a single bolt from a quarrel, a stab with a sword, etc should severely cripple Garret, making running away much more difficult due to reduced movement, limping, a trail of blood, etc. However, in the original Thief, Garret was extensively trained in the art of swordplay by the Watchers. One on one Garret should be more than a match for any guardsmen, with their armor being the only mitigating factor, making them tougher.
I'm not saying straight up assaults should be the way to play Thief at all, just that Garett should be a superior swordsman than your average guard. Ofcourse the game world could have other characters, like duelists & blademasters who are better than Garret one on one.
No, the main obstacle to a good Thief game is that Looking Glass Studios is no more.
This too.