Currently in the game there are three jobs that can be done in the Mansion without a tool to accompany it.  Prostitution, Alchemy, and Cooking.   I fail to see the reason why Alchemy and Cooking don't use the Hunting knife, in cooking one often has to use a knife to cut meat or vegetable and in alchemy many of the recipes use blue moss or salvia which should be chopped up with a knife to make into workable pieces, or to carve the runes into a magic staff.  Could also possibly add a new upgrade to the mansion that is a Mortar and Pestle that increases alchemy and cooking (limited to grain recipes,  and maybe a still that increases the number of alcohol produced by one per craft.

 Of course putting a tool for use in Prostitution isn't exactly easy, as none of the tools exactly belong in the bedroom, Though if there were prostitution bonuses added to the sexy Lingerie and see through lingerie and stimulating lingerie it would make sense.