Yeah, unfortunately there isn't a wide range of sounds you can use that is "out of character" (Arngrim picking locks?) so I had to resort to re-using some sounds.Lenneth shouldn't be too much of a problem, but I'm not sure the others have enough suitable lines to make a full soundset. Especially the pick pocket/hide/trap set bits seem iffy. I think that's what ultimately made me give up on making my own VP soundsets. Back in 2005 or so. (Holy shit.)
...I remember the quality varying between clips, too - certain sounds are much more compressed than others, for... I have absolutely no idea what the reason could be.
And yes, the some of the sounds that are used in battle are more compressed than the story mode ones. They probably did it to save memory on the PlayStation because the sounds would be played dozens of times (i.e. when hitting the enemy).
If one were so inclined, it is possible to take the sounds from the PSP version (which is just a re-release of the original VP) because they digitally re-mastered *some* of the audio and voiceovers.