Yes, it can be done. I have a 64GB flash drive here, with 9 partitions. I currently have separate, bootable partitions for all installers from Leopard to Sierra, and enough space on the last partition for the next couple of major releases.
Is it particularly useful? Maybe as a curiosity, more than practical. I have found that it doesn't really take long to burn out a bootable installer from the collection of installer apps that I keep.
But, it's kinda fun to keep that stick in my pocket, and I can boot/install any supported macOS on any Intel Mac, all from that one flash drive.
I also like the SD card idea...