Hello,
As far as the Wiki page states, "Up to 3 hexes from opponent, your character is always visible, regardless your sneak skill," unless any of this has been changed with the wipe.
I have wanted to play a thief character, and while I know thieves are despised enough already, I think a skilled thief should be able to sneak away with loot undetected after a successful Steal. Stealing while being seen completely takes away the fun of it for me, and I feel like it is a slap in the face to the players being stolen from.
While the current system may be acceptable for stealing from NPC's, I think the only way to steal from other players should be when they cannot see the thief. Because let us be honest, it is silly to just stand there as we see someone going through our pockets, and we should not allow that to happen.
That is why I think that when one's Sneak is high enough, they should have a chance to reach another player undetected. It would all be dependent on the opponent's perception and peripheral vision (which way their character is turned), and of course the sneaking character's Sneak skill.
That way, the limit could stay 3 hexes away in the opponent's field of vision directly in front of them, but as one's Sneak is being improved they could be able to sneak up to an opponent 2 hexes away from behind, then perhaps 1 hex from behind and 2 hexes from the sides, and eventually if their Sneak is quite high, they could stand in the hex directly behind another player undetected, and within 1 hex away from the sides or 2 hexes from the front.
(Maybe later on they could sneak up directly from the sides as well or even the front when Sneak is 300, but the details could be hammered out later.)
Still, if they attempt to steal and the steal is unsuccessful, it would make the opponent detect them.
On top of that, perhaps stealing could be made 'hardcore,' and the only way to successfully steal from another player would be in Sneak. Any Steal performed on a player while not sneaking would automatically be unsuccessful, and any unsuccessful steal would automatically break Sneak. To make things even more complicated, there should be some kind of a system to prevent thieves from just repeatedly trying to steal from the same player over and over until they get lucky. Perhaps a time limit during which the thief would always be visible to the player, even in Sneak. Or perhaps the thief would at least have to exit the current location and come back. As for stealing from NPC's, I guess the current way is fine since it is not as big of a deal to steal from them, but again, that is something that could be decided on later.
I think this would make a thief character a lot more challenging but also a lot more fun to play for dedicated thief players. At the same time I believe it would reduce the amount of 'troll' thieves waiting in towns to rob players speaking to traders or just wanting to peacefully go about their business. One would not have to automatically get nervous and jittery for fear of being robbed whenever another player runs too close to them.
The only thief they should fear is the one they cannot see.