personally I like the idea of giving Vulps a good sense of smell, How I would like to see it done if at all possible is:
firstly allowing them to smell blood, have blood and bloody objects produce some sort of gas which is visible to vulps and can be toggled on and off (because it would get annoying sometimes)
secondly if you want to be able to smell your crew mates I suggest having a similar thing as the blood where they produce gas that you can attempt to follow.
Thirdly allow showering to completely wipe away your scent for about 20? minutes, to stop sec and stalker vulps from being overpowered as hell.
Fourthly only because the OP suggested it, have lings produce a slightly different amount of scent than the original. so only the most observant people in the community could notice. Also this means that returning to places that the original visited a lot (where his scent would be) makes it impossible to know and of course they can shower.
Final its probably way to much work to code and will probably cause a bit of lag, BUT I CAN DREAM CAN'T I!?