I think winimage can do this, load the windows 98 iso into winimage, than select something to do with bootable cd, and select the windows 98 bootdisk image. it should make an entire new iso that is bootable.
im not 100% sure , But I think im right, because the way that most cd boots with a bios is it uses floppy emulation. at the beginning of a the cd theres a hidden directory (boot) or something like that , that has a floppy image. So I believe winimage can make a iso bootable, by adding a boot floppy to the iso.
Winimage.com, as the title suggests, is falsely flagged. winimage is a tool used for manipulation of virtual CD and floppy images for use in programs such as vmware, say, you want to quarantine a virtual machine because you may have gotta a virus but need to put something on it to find out, you could use winimage to create a read only CD with said tools.
According to winimage.com, "WinImage is a fully-fledged disk-imaging suite".
In our case, we can use it to write a Mageia iso on a USB stick.
Its main advantage, for our purposes, is that it can work in environments with restrictions, like Microsoft Windows 7 Starter.