I've updated a 5 year old idea: https://www.raspbian.org/RaspbianInstaller
The links below are for raspbian stretch:
ARMv6 (pi 1) https://1drv.ms/u/s!AvHY_kl4hMB4fbwbN27_IRQLerE
ARMv7 (pi 2 and 3) https://1drv.ms/u/s!AvHY_kl4hMB4fpZr8wn3u8623Uc
These were built in raspbian using the debian-installer package (i.e. not hacked together). I've kept changes from real debian armhf to a minimum so you'll have to select the manual partitioning option and sort out the bootloader yourself (just like my lubuntu iso viewtopic.php?t=190511 ).
The installer uses (and by default installs) the linux-image-rpi* kernel package. You'll have to add the archive.raspberrypi.org repo if you want any of the packages from there. You'll also have to add contrib, firmware, non-free and rpi.
There is lots of info out there about how the debian installer works, the vast majority of which should apply here.