Does the BIOS support a network boot? Are all of your systems of the same type? This one of the things that needs to be considered to determine how to setup a boot server(s).
Wikipedia has a network booting article that provides some information about the process. You'll need to take a look at your BIOS documentation to better understand what can be setup and how it is done. It may be necessary to enter network information into the BIOS on each server for instance.
Note that while the GRUB PXE documentation allows for a network boot, the GRUB bootstrapping code it still expected to be accessible somewhere on each system. Since your servers are diskless, this means that this code must be accessible via a bootable floppy or other media source.
Unfortunately either it way the process is probably not to be as automated as expected.
Fedora also has a couple of documents you should take a look at: Booting from the Network using PXE and Setting Up an Installation Server.
In terms of network traffic, how is each server to save files? Certainly things like logs will need to be stored somewhere remotely. The amount of traffic could be substantial depending on certain situations such as when debug settings are enabled or high activity, however this is atypical and dependent on how things are configured plus the environment.
I would certainly try to trim the system (OS, applications, ...) as much as possible to reduce network usage if this is a concern, but suspect that this might ultimately be lower on your list of concerns.