FAT32 / NTFS + isofs on USB flash drive

I have a bootable USB stick as shown in the screenshot: # dd if=/path/to/os_image.iso of=/dev/sdb (...everything OK...) # sudo dumpe2fs /dev/sdb dumpe2fs 1.42.9 (4-Feb-2014) dumpe2fs: Bad magic number in super-block while trying to open /dev/sdb Couldn't find valid filesystem superblock. GParted doesn't recognize any partitions. The GUI file manager reports the filesystem as isofs. The system boots and everything works fine. The problem is, I want to use the USB stick for a live OS _and_ as a storage with PCs and TVs which only recognize FAT32 and NTFS. I have tried creating two partitions, doing dd on sdb1 and making sdb1 the only bootable partition, but the system didn't boot. How to put both FAT32/NTFS and (any) bootable ISO image on an MBR-partitioned disk without using an external bootable USB creator program? I would like to simply use dd, as I do now. Presumably this could be solved using the right bootloader with the right configuration. I just don't know which bootloader and what configuration.