Someone at the RRF (Jeff Scott?) put toasters in both positions of a 4004 a few years ago and he was satisfied with the tone. OTOH that won't make it sound like a 4001/4003, and neither would putting a toaster as a third pickup on a 4004.
I had a 4004 and 4003 at the same time, the weight difference sure didn't seem like much to me.