+1

The mtools/mformat are not AFAIK released pre-built for Windows, in case of need here is a build:

http://reboot.pro/topic/14354-buidlingmodifying-floppy-image...

Syntax/option for mformat are a bit complex, again in case of need here is a small batch that hopefuly makes commands clearer:

http://reboot.pro/topic/21664-makeiso/page-4#entry205455

There's also genimage [1] which uses mtools for FAT, but it can also do ext2 and more.

[1] https://github.com/pengutronix/genimage

That looks like it might work, thank you. My search did not find this.