Flash memory is not designed to be a medium to which intensive writes
occur. However, anything up to and  including writing stuff down
longhand is better than floppies. ;)

Since the original question was if an USB flashram stick could be used
instead of a floppy, the answer to that would be no right - since the
question seems to be whether or not just the floppy could be replaced
that way, while still booting from CD? That is how I read it anyway.

A better way would be to buy an IDE flash ram module from Transcend. A
small one will do so we're not talking much money either. Then just
install the m0n0 image onto that and use it like a "hard drive" and
presto you've done away with the need for either the CD, the floppy or
any USB flashram.