Would completely bypass the iSCSI setup, and each machine would still get the latest image from your server before the lan party begins.
There have been a decent number of times when I actually did this during a party to fix an issue, or between parties just to keep the machines maintained for the family to play with, etc. It'd be hard to do that if I have to spend hours transferring a large image every time.
Aside from the stability issues at boot time, there isn't really a down side. I don't have any problems with load times. So I'm pretty happy with the setup.
Also, maybe having a steam cache server and using the local disks as a game store might help with installation of games?
Definitely can see the benefits of the netboot setup, though!