Quasqueton said:
Well, for instance, how do you handle it when the PCs want to disarm their opponent?
When a PC reduces his opponent to 0hp, he gets to decide what that means. If he wants it to mean "dead" then the opponent dies. If he wants it to mean "unconscious" then the opponent is unconscious (or has a certain chance of being unconscious rather than dead, DM's option), if he wants that to mean "disarmed" then the opponent is disarmed, if he wants that to mean he has pushed his opponent over a cliff, then over he goes. Hit points represent how tough an opponent is to "defeat", not necessarily how much physical damage an opponent can withstand (they were always meant to be an abstract concept). I think it's a mistake to incorporate "moves" that provide a work-around for reducing an opponent's hit points.
As for the other things you asked about some of them are already covered by the rules. For example, thieves may be the only ones who can move
silently (i.e. creating NO noise), but anyone can attempt to move
quietly. There are rules for when non-thieves can "hear noise" (1 in 6 for normal humans, 2 in 6 for demi-humans), so I would simply have whatever guards the PCs are attempting to sneak past make "hear noise" rolls with appropriate modifiers for the situation (if the PC party contains people in heavy armor or who are heavily encumbered, the chance that the guards hear them would go up slightly).
The same is true for a magic-user attempting to hide. Thieves get to
hide in shadows. While an M-U cannot do that, he can easily conceal himself behind a barrel or in some bushes. If I, as DM, decide that there's a certain chance that he might be noticed anyway, I'd roll a surprise check for his opponents (with appropriate modifiers factoring in how well the M-U had chosen his hiding spot). If the opponent was "surprised" it would represent the M-U going unnoticed. If the opponent wasn't "surprised" it would represent him spotting the M-U. IMO this isn't necessarily a "house rule" or "rules patch" because it's obvious what surprise is intended to represent within the rules and that this falls within that category.
As with any game (including 3e) it does no good to have a rule to cover a situation if the people reading/playing the rules don't take the time to learn and understand them.