Hi, when recycling old pickups I sometimes have used a 6 string single coil under three strings, it works ok but does not look the best. So what I do is as in the photo below. I bought a bunch of pickup covers without the holes and fitted them instead. Now they don't stand out as not matching the strings.
Awesome idea! Bet you could glue the lid cutout of the cigar box to the top of that.
A lot of the Chinese made pickups have pickguard material top covers with holes punched for the pole pieces or you could have no holes or cut designs in it for a decorative look.