Felix said:Add another level of mechanics so that you may expunge one small part of the existing mechanic?
What, "the character perceiving gets +2 to their roll because it's easier to notice someone than to remain perfectly silent and hidden" counts as "another level of mechanics"? Especially when you're deleting something like half a page of text (2 full skill descriptions) into the bargain?
Not to mention that there's already a precedent for this, as noted above.
My DM must lay more ambushes for the PCs than yours does.
If your DM really wants you to get snuck upon, you have no hope, implied probabilities or no.