In the shave of the day there was someone who used "Gentleman Jack" by Jack Daniels, straight from the bottle, as an aftershave, with success.
Also, most whiskeys are very aromatic, when the alcohol has dissipated(after a few minutes) the aroma stays, and it doesn't resemble a "You've been drinking just now"-smell.
I think the whiskey in itself(with perhaps some glycerin) is a fine aftershave. The bay leafs in Bay Rum are aromatic(and have some topical properties) mostly. And using a lot of spices makes the Bay Rum smell great.
But(good) whiskey is different, in that IMO it is drunk mostly straight up, maybe just some whiskey+lemon peel+ginger will make a good aftershave.
Maybe an Islay(smokey) whisky will be suited the best for this, as it is the furthest removed from rum and has really specific(MANLY!!!!) aroma's.
Well... I'm gonna marinate on it.