"Can you tell me how can I make a system where I boot from tomsrtbt and them swap it with the floppy containing DosEmu/FreeDOS"
After you boot tomsrtbt and login then you can remove the tomsrtbt floppy. Then you can mount the floppy containing dosemu with commands similar to:
mount -t ext2 /dev/fd0 /possum
when you are finished with that floppy:
and mount the next floppy that you want to use.
dosemu is probably too big to fit on one floppy. I don't know how you will arrange the floppies for dosemu, FreeDOS, and your DOS application programs so that all of this will work. You will have to experiment to find out the best way to arrange things.
You could greatly simplify the problem by leaving out Linux and dosemu. Just boot FreeDOS on a bootable floppy. Your DOS application programs can be on a second floppy and you can switch the floppies as needed. I have run this way in the past and I still have a working DOS bootable floppy than I can use to run DOS whenever I want.
Be prepared. Create a LifeBoat CD.