There is an alternative that works in some cases: DOSBox 0.74 can't change mounted floppies on the fly, but it can change mounted CD images on the fly. What you do is burn the files from each floppy disk into a different .iso image, and then mount all the .iso files using the IMGMOUNT command, as described in the DOSBox readme.
But it doesn't always work: some installers look at the floppy disk volume label of the install floppies. You can of course change the ISO9660 volume label of the .iso images as well - but the .iso creation program might try to strip out certain characters (like "#") which you would have to hex-edit in manually. And of course some installers just won't accept that the files are coming off what appears to be a CD-ROM instead of what appears to be a floppy drive.
And of course it's a fair amount of effort for something that might not work at all, especially if you already can't manage to get it to work with Virtual Floppy Drive.