That's an unnecessary expense (or my labor) when the bottom hole is already there. When the logic board is removed the black back plate comes out too so that is where the air would then come in. Just turn it upside down and add some stick-on rubber feet from the hardware store (or Amazon).My suggestion is to remove a circular portion of the Mini top surface
As you said, the only thing necessary would be a foam filter and that is what I will try first -- and add the fans only if needed (USB powered). It definitely will have a front-facing power button mechanism though.